TETR.IO

TETR.IO
TETR.IO logo
Developer(s)	osk
Designer(s)	garbo GlitchyPSI (Assisting)
Programmer(s)	Dimentio Dr Ocelot flash (Assisting)
Platform(s)	Web (Native) Desktop: Windows, Linux, macOS
Release	INDEV February 19, 2019 INFDEV January 31, 2020 Alpha March 22, 2020 Beta July 26, 2024
Latest release	Beta 1.0.0 / July 26th, 2024 Desktop V9 / March 9th, 2024
Gameplay info
Next pieces	1~6 (default 5)
Playfield size	10 × 40 (default, modifiable in custom single-player and multiplayer games)
Hold piece	Yes (default)
Hard drop	Yes (default)
Rotation system	SRS, SRS-X, SRS+, ARS, NRS, ASC, Tetra-X, None

TETR.IO is a free-to-play online multiplayer and single-player game developed by osk. Players can play against friends and foes all over the world and claim a spot on the leaderboards, found in the TETRA CHANNEL. It is referred to as a free-to-win, modern yet familiar online stacker game in the same genre as Tetris.

Multiplayer

In multiplayer, the player can play online multiplayer games against other players, exactly as it says on the tin. A player can choose to play in the game's Quick Play room; alternatively, the Custom Room option allows for creation of public or private rooms, with the ability to change settings for the room such as spin bonuses, player limit, the amount of next pieces shown, and others. The player can view public rooms in the Room Listing menu, if the host of the room set it as a public room. Each multiplayer game with 3 or more players plays similarly to Tetris 99 along with alike targeting options, minus the ability to manually target by default, included. A garbage/gravity margin time system is also in the game, in which the amount of garbage sent/gravity present on the active piece is multiplied more and more after a static period of time.

Mechanics

Including modern stacker staples such as Garbage (notably using "change on attack" randomization rules), Gravity, and the quintessential Line clear, TETR.IO contains several miscellaneous mechanics that offset it from other games.

Combo System: "Multiplier"

An illustration of the combo table in use, as well as an explanation of the "B2B Chaining" mechanic. Yellow cells indicate the attack shown is strong enough to cause a "spike", red cells indicate that the garbage sent would be enough to cause a topout if garbage is not countered, and purple cells indicate an attack which is large enough to cause a "spike KO"

All multiplayer TETR.IO matches utilize a very different combo table than other Tetris games and clones. This system is known as the multiplier system in the community, and its purpose is pretty simple. It heavily nerfs the previously overpowered "four-wide" combo setup, and awards combos with Quad or T-Spin finishers with a large spike. This system cannot be disabled or altered in any way, and it is present in every online match including Quick Play, Royale and TETRA LEAGUE. Multiplier is the default combo attack table setting for Custom Rooms, although it can be changed to another combo attack table.

Back-to-Back Charging

Back-to-Back Charging is a mechanic added in the Beta 1.0.0 update alongside the new Quick Play mode. This is a default mechanic used in multiplayer games as of the Season 2 Pre-Season, replacing Back-to-Back Chaining.

To take advantage of this mechanic, one must do several "difficult line clears", meaning Quads, T-Spins and All-Spins if either the All-Mini or All-Spin allowed spins setting is chosen, without clearing singles, doubles, or triples inbetween each difficult line clear. This is known as Back-to-Back, and they are rewarded in other Tetris games and clones by adding one line of garbage to an attack.

When a player gets a Back-to-Back streak of 4, they will begin charging up a Surge attack with a starting power of 4 damage. Any difficult line clear at a B2B streak of 4 or higher will increase the power of their Surge attack by 1, so a higher B2B streak rewards the player with more Surge attack. For example, if a player has an 8 B2B streak, they will have a Surge of 8 ready. Quick Play handles this differently however, with a starting Surge attack of 1 rather than the usual 4.

The Surge Attack is released with all of the player's stored Surge damage being sent to opponents when they break their B2B streak. It is split into three segments of attacks with the first and/or second grouping into a larger chunk if the surge isn't a multiple of 3.

Back-to-Back Chaining

Back-to-Back Chaining was introduced in the 2.3.2 update released on the 24th of April, 2020 as an experimental feature which quickly became a popular quirk for many, and made its way into being a default mechanic the next update the day right after it was introduced, before being replaced with Back-to-Back Charging in Beta 1.0.0 and Beta 1.1.0 for the Tetra League Season 2 Pre-Season.

Back-to-Back Chaining rewards the player according to how many difficult line clears one can clear in a row:

Range of concurrent, unbroken "difficult line clears" done in a row	The corresponding visual "B2B" indicator shown	Garbage added to the line clear's normal garbage amount
0-1	(none shown)	0
2-3	B2B x1-B2B x2	1
4-8	B2B x3-B2B x7	2
9-24	B2B x8-B2B x23	3
25-67	B2B x24-B2B x66	4
68-185	B2B x67-B2B x184	5
186-504	B2B x185-B2B x503	6
505-1370	B2B x504-B2B x1369	7
1371-3725	B2B x1370-B2B ×3724	8

Supposedly, this system stretches on into infinity, as it seems to progress similarly to a square root function. Values up to level 8 were posted by osk in a pinned message on the official TETR.IO Discord server's #tetrio-general (formerly known as #tetrio) channel.

This system can be disabled in a custom room by the room host, with the small ON/OFF toggle at the bottom of the game settings labeled "Enable Back-to-Back Chaining". Although it was replaced with Back-to-Back Charging as the default setting as of the Season 2 Pre-Season, B2B Chaining can still be enabled alongside with or in place of B2B Charging by custom room hosts.

Garbage Travel Speed: "Passthrough"

As another big deviation from other clones and official games, this mechanic allows two players to send garbage to each other without negating the garbage sent if timed correctly. If this system is enabled, a timer of 20 frames, or 333 milliseconds plus a variable amount of network lag, begins whenever any player sends garbage. During this timer, the garbage sent is untouchable, and any garbage sent from the player this garbage is going towards will pass through to the enemy targeted without interrupting the garbage coming their way. In this case, a special sound will play, and the garbage sent will land on the user targeted entering their garbage queue.

As of 6.1.2, hosts must opt-into this system, by toggling the "GARBAGE PASSTHROUGH" option, which is disabled by default, under the "GRAVITY AND MARGIN TIME" category. This mechanic has, historically, gone through many controversies leading to its removal as a mechanic by default -- please refer to the Professional Concerns section for more info.

Quick Play

Quick Play is the main free-for-all room in TETR.IO, aiming to be a more casual, unranked experience, and was revamped in Beta 1.0.0. The goal of this mode is to climb as high as possible and battle it out in a large free-for-all lobby. Upon being eliminated, players can promptly start a new run without waiting for the game to end. There are two leaderboards for Quick Play that reset weekly: Quick Play and Expert Quick Play (Expert mod enabled).

Floors

Zenith Tower, the stage of Quick Play, is divided into ten floors by height. Reaching a new floor, other than floors 1 and 10, for the first time unlocks a new mod.

Floor	Name	Height range(m)
1	Hall of Beginnings	0–50
2	The Hotel	50–150
3	The Casino	150–300
4	The Arena	300–450
5	The Museum	450–650
6	Abandoned Offices	650–850
7	The Laboratory	850–1100
8	The Core	1100–1350
9	Corruption	1350–1650
10	Platform of the Gods	1650 and above

Climbing

Players climb the Zenith Tower by sending lines and eliminating other players.

Climb speed is gained by sending and cancelling lines, indicated by the shapes under the player's board. You start at level 1 and there is no cap. You climb at +0.25m/s per level of climb speed passively, starting at 0.25m/s. Climb speed decays constantly, decaying faster at higher climb speed levels. When levelling up, this decay will pause for a certain amount of time which is shorter at higher levels.

Sending, but not cancelling lines, will gain bonus altitude, shown as a flashing +NUMBER above your username. Each line sent immediately boosts you by 1 second of your climb speed. KOs are equal to 15 lines, but do not contribute to climb speed progress.

In Expert Mode, climb speed builds slower and decays faster, and cancelling lines does not contribute to climb speed progress.

Level	Color	Total permanent garbage	Garbage received	Message
8 minutes	+2 permanent lines	2	1×	Fatigue sets in...
9 minutes	Receive 25% more garbage	2	1.25×	Your body grows weak...
10 minutes	+3 permanent lines	5	1.25×	All senses blur together...
11 minutes	Receive 25% more garbage	5	1.5×	Your consciousness fades...
12 minutes	+5 permanent lines	10	1.5×	This is the end.

Hyperspeed

When the player reaches a certain climb speed level specific to each floor before reaching floor 6, the player enters Hyperspeed. In Hyperspeed, a speedrun overlay shows up with the player's progress, the time the player completed each floor, and their best times. To enter Hyperspeed, the player must reach either climb speed 8 on floors 1 or 2, level 9 on floors 3 or 4, and level 10 on floor 5. You cannot enter Hyperspeed after floor 6. Hyperspeed ends when the player reaches floor 10 or fall below climb speed 6.

Fatigue

When the player's run goes on for too long, the player receives a debuff every minute starting from 8 minutes up to 12 minutes. These debuffs stack and last until the player tops out.

Time	Debuff	Total permanent garbage	Garbage received	Message
8 minutes	+2 permanent lines	2	1×	Fatigue sets in...
9 minutes	Receive 25% more garbage	2	1.25×	Your body grows weak...
10 minutes	+3 permanent lines	5	1.25×	All senses blur together...
11 minutes	Receive 25% more garbage	5	1.5×	Your consciousness fades...
12 minutes	+5 permanent lines	10	1.5×	This is the end.

Mods

Quick Play features a total of ten mods that can be enabled before starting a run. Nine of them are unlocked by reaching a certain floor, and one of them, the Duo mod, requires TETR.IO Supporter. The unlockable mods have effects such as disabling hold pieces, making some garbage lines have two holes on them, increasing gravity, etc. With the Duo mod, two players play together as one team with each player having their own board. If one of them is eliminated, the other player can revive them by doing three random tasks.

Mod name	Effect	Unlock condition
No Hold	Disables the ability to hold pieces.	Floor 2
Messier Garbage	Garbage is significantly messier.	Floor 3
Gravity	Gravity increases greatly for every floor reached.	Floor 4
Volatile Garbage	Receive and cancel double the normal amount of garbage.	Floor 5
Double Hole Garbage	Garbage may sometimes spawn with two holes.	Floor 6
Invisible	Non-garbage blocks become invisible and are shown briefly every 5 seconds.	Floor 7
All-Spin	Spins with non-T pieces are considered full spins instead of mini spins. Performing the same clear or action twice spawns wound lines that are unaffected by Double Hole or Volatile mods. Action text stays on-screen after any action is performed.	Floor 8
Expert Mode	Lowered garbage delay. All garbage lines enter at once instead of rolling in one by one. 0 Combo Singles send no lines of attack compared to one line. Cancelling garbage does not contribute to climb speed.	Floor 9
Duo	Allows two players to play as a single team.	One player must be a Supporter

Wound lines

Wound lines on a player's board.

When a player performs the same clear or action at least twice in a row with the All-Spin mod enabled, a type of unclearable garbage lines spawns on their board, called wound lines. Wound lines consist of blocks that change color and have a number indicating how many clears one must perform before they turn into regular garbage. The number of clears required increases as the player reaches higher floors.

Royale

Royale, formerly known as Quick Play, is another free-for-all room in TETR.IO, which, since Alpha 6.4.0, uses the ROYALE game mode with a dynamic garbage queue depending on the number of remaining players. Prior to this version, the standard versus format was used, with fixed, less forgiving garbage mechanics.

Tetra League

An illustration of the Season 1 Tetra League mechanics. Currently outdated as of August 2024.

Tetra League is the ranked mode in TETR.IO. As of its public release, players must be registered and their level must be at least level 10 to enter, and anonymous players cannot play this mode. When the mode was first released, INFDEV testers and supporters were only eligible for the mode. Each game of Tetra League is a 1v1 match, with a first-to-3, FT5, or FT7 format based on the highest ranked player's rank. The rating system is called Tetra Rating, which is based on Glicko-2. TR increases for each win and decreases for each loss exclusively. When playing this mode for the first time, the player must play at least 10 ranked matches, referred to as the "rating games", to display their TR. A letter rank is assigned to all players with less than 100 RD (short for Rating Deviation) based on their percentile in the leaderboards. RD normally decreases to a lower limit of 58 RD every time the player plays a Tetra League game, and slowly increases at a flat rate of 1 RD per day after a week of inactivity, leading to a maximum of 350 RD.

Solo

The game also includes solo modes, two of which have leaderboards: 40 Lines and Blitz. For all modes except Zen, Stride Mode can be activated. This option speeds up the countdown by changing it from "3-2-1-Go" to "Ready-Set-Go", enables tap-to-retry (by default, players will have to hold the retry key to do so), reduces the time to exit a solo game by holding the forfeit key, speeds up all animations at the start and end of games, and prevents the first piece from being either S, Z, or O except in Custom Games. 40 Lines and Blitz also have an option called Pro Mode which shows the finesse counter if the slot used is set to default. In 40 Lines, it displays the number of lines remaining on the board and the total keypresses as well as keypresses per piece on the left, while Blitz features a timer on the board.

All solo modes have a scoring table similar to the ones seen in guideline games. It goes as follows:

Line Clear/Action	Points Scored
Single	100
Double	300
Triple	500
Quad	800
Spin Zero	400
Spin Single	800
Spin Double	1200
Spin Triple	1600
Spin Quad	2600
Mini Spin Zero	100
Mini Spin Single	200
Mini Spin Double	400
Mini Spin Triple	800
Mini Spin Quad	1600
All Clear	3500
Back to Back "difficult" line clears	$x*1.5$ (where $x$ is the point value of the line clear)
Combos	$x*50$ (where $x$ correlates to the current combo value)

All point values are multiplied by your current level, except for Zen mode, where no level multiplication occurs.

In addition to this table, there are flat rates, which are not multiplied by level, for simply dropping a piece as well:

Action Taken	Points Scored
Hard Drop	2 per cell dropped
Soft Drop	1 per cell dropped

40 Lines

In 40 Lines, the objective is to clear 40 lines as fast as possible. In accordance to TETR.IO's delayless vision, no "stacking style" limits your speed thanks to the lack of ARE and the presence of "0ARR" handling settings.

Blitz

Blitz is similar to Ultra, requiring the player to score as many points as possible within two minutes. Unlike Ultra, there is a level system present similar to Marathon with a variable line goal before increasing the level:

Level	Lines required to level up	Total lines cleared	Gravity (seconds per row)	Gravity (G)
1	3	3	1.0	0.0167
2	5	8	0.643	0.0259
3	7	15	0.404	0.0412
4	9	24	0.249	0.0670
5	11	35	0.150	0.111
6	13	48	0.0880	0.189
7	15	63	0.0505	0.330
8	17	80	0.0283	0.588
9	19	99	0.0155	1.08
10	21	120	0.00827	2.01
11	24	144	0.00431	3.87
12	26	170	0.00219	7.62
13	28	198	0.00108	15.4
14	30	228	0.00052	20
15	32	260	0.00024	20

Higher levels are possible, but omitted for brevity. You can replicate this leveling scheme with the "leveling speed" option in custom solo games set to "0.42" and "base gravity" set to "0.65". These values were ripped out of a .ttr file of a Blitz replay. In it, it defines the level speed value and can be technically read with any conventional text editor, as the file itself is plain text JSON data.

Unlike most of the game however, Blitz still doesn't have All-Spins and therefore only regular three corner detection T-Spins count for extra scoring.

Zen

Zen is an endless mode with no top out game overs and a special level system, inspired by the mode of the same name from the Bejeweled series, starting with Bejeweled 2, where it was named Endless. Gravity is adjustable by the player, and garbage is toggleable from a menu accessible after hovering over the right side of the window. It can also be played while waiting for the next match in Quick Play, Custom Rooms, or while waiting for your next opponent in the TETRA LEAGUE queue. Experience Points are gained at a static 100XP per minute whilst in Zen mode. This caps to a maximum of 3000XP per session sometimes, meaning one can only gain Experience Points for a maximum of 30 minutes before needing to forfeit and re-enter Zen mode to continue receiving Experience Points.

Custom

The player can create their own solo mode with most of the settings carried over from the Custom Play room creation menu. By default, the Custom Room options are set to match those of the fixed-goal Marathon mode from Tetris games.

Badges

Main article: TETR.IO/Badges

Badges are given to registered TETR.IO users to immortalize special accomplishments on their profile. Badges are typically rewarded for placing highly in organized tournaments and events, for extremely difficult and rare feats in game, or as rewards in exceptional circumstances.

Some badges, such as Secret Grade, 20TSD, and 10PC have been superceded by achievements as of Beta 1.0.0, and as such are no longer obtainable.

Rotation System

180 Kicks

A diagram of TETR.IO's 180 kicks, as posted, and pinned, by osk on the official TETR.IO discord server in the "#tetrio" channel.

Starting with 0.6.0-pre0, TETR.IO made its first non-guideline modification to the kick table, adding a custom 180 kick table. This table is relatively resilient to abusable spins, however there is plenty of room for handy L and J tucks with this system.

In a situation shown to the left, limited to guideline clockwise and counterclockwise spins, the only "clean" downstack would be building up a wall on the left side of the field and spinning a Z in.

Like so:

However, if you have a 180 key bound and a L tetromino in the playfield, simply soft drop,

and 180!

SRS-X

TETR.IO also includes a separate kick table known as "SRS-X" that can only be enabled at the request of a room host or a solo custom player as it is not the default kick table. SRS-X is known for its "more powerful 180 spins" such as the ones seen in NullpoMino or the Heboris Unofficial Expansion. Aside from that, it is standard SRS with no modifications.

SRS+

A very simple graphic detailing TETR.IO's SRS+'s symetric attributes, as posted, and pinned, by osk on the official TETR.IO discord server in the "#tetrio" channel.

As of version 5.0.0, TETR.IO uses a modified version of SRS as the default option, in which the I wall kicks are symmetrical along the y-axis, similarly to TGM3; however, the left-side kick tables are mirrored instead of the right side. This allows certain situations that are impossible in regular SRS to be made effectively.

As in Guideline SRS, the shown placement can be achieved by rotating clockwise.

In the symmetric position, this can now be achieved by rotating clockwise or counter-clockwise.

TETRA CHANNEL

The in-game TETRA CHANNEL contains leaderboards with replays for 40 Lines and Blitz, weekly leaderboards with temporary replays for Quick Play and Expert Quick Play, and your last submitted solo, Tetra League or Quick Play replays in the "ME" section. The Players screen lists the top players sorted by their league rating, achievement rating or by the total amount of experience points (XP) accumulated throughout the game. Leaderboards are also capped at the hundredth player.

In addition to the features above, it also shows players who are currently streaming with the TETR.IO category on Twitch. The Tetra News section displays achievements done by players, such as reaching the top ten in either solo mode with a leaderboard, or winning one of TETR.IO's many partnered tourneys. There is also a simple "search bar" at the top of the TETRA CHANNEL, where you can input specific replay IDs or URLs to access them, as well as access specific player cards with a username or User ID.

Standalone TETRA CHANNEL

After the 5.0.0 update, a standalone TETRA CHANNEL site was released. This site would accomplish most of the same things the ingame TETRA CHANNEL would do, with the added benefit of more detailed userpages, extended leaderboards, free access to anyone without an anonymous or registered account, and more detailed server statistics. Specifically, solo leaderboards would be extended from the top 100 times to every user's personal best, the TETRA LEAGUE player leaderboards would be extended to every ranked player, and the XP leaderboards would be extended to every player above level 100. Furthermore, all "player leaderboards" could now be filtered by specific countries as well.

A similar "search bar" to the one found in the ingame TETRA CHANNEL is present in all pages on this site as well. This search bar will only accept exact usernames and User IDs, and when utilized, takes the user to the requested userpage. A userpage is far more detailed than their ingame player card counterpart, and includes highly detailed information about a given user's 40 Lines, Blitz and Quick Play personal bests, as well as links to their top replays in all solo modes, and their most recent submitted replays in the last seven days (30 if they have supporter). Additionally, TETRA LEAGUE statistics and all Tetra League match records can be found here, coupled with a simple Zen mode counter signifying what score and level a user has.

An extended "Tetra News" section would be included with this site as well. Normally, from the front page, the Tetra News section mirrors that of the Tetra News from the ingame TETRA CHANNEL. However, below all of the "global news" lies a button labeled "VIEW ALL". This link will take you to a dedicated Tetra News section of the site, where a news ticket is created whenever any registered user gets a new personal best, ranks up to a "top rank", meaning this is the first time they've ever been in that given rank during the season; and achieving any of TETR.IO's many badges. This page will only fetch the last 100 news events, and updates on its own whenever new news events occur. These news events are known as "Local News", and show up on the newsholder's userpage long after they expire from this global local news section.

Reception

Promotional material created by osk for display on the @tetriogame Twitter account, to celebrate the latest New Year's Day.

You can always fetch a list of various extremely up-to-date stats from the TETRA CHANNEL's main page, including, but not limited to: the exact amount of registered players split up into three categories, global time spent playing TETR.IO across all games, how many of those games have been played and completed, and miscellaneous stats such as pieces placed and how many keypresses total.

On the 3rd of November, 2020, TETR.IO reached the milestone of half a million players. This milestone was celebrated with a "triple XP week" which, as the name sort of implies, tripled the XP players gained for the time the celebration ran.

TETR.IO hit a total of one million players on the 9th of February, 2021. This milestone was celebrated by, once again, temporarily multiplying the XP amounts players gained for the week of the celebration. This time, XP would be quintupled for the first day, then tripled for the rest of the week.

Later on, TETR.IO would reach a total of two million users on the 31st of May, 2021. As well as the same XP multiplication as last time, 500% for one day, then 300% for the rest of the week, users would also be treated to a 25% off discount on TETR.IO Supporter for the entire week. This discount stacked with the regular discounts for buying gifts, or buying in bulk.

Continuing the streak, TETR.IO would celebrate the 3 million player mark on the 17th of September, 2021. This time around, the XP multiplication hit 300%, and TETR.IO Supporter was 30% off instead of 25%. These discounts and boosts would expire just 3 days later, this time around.

And, more recently, TETR.IO's playerbase would make the mark of 4 million players on the 8th of December, 2021. Staying true to form from the previous milestone, players were treated to 400% XP generation, as well as a 25% TETR.IO Supporter discount for only one day.

Professional Concerns: The Removal of Passthrough

Results of the completed passthrough.osk.sh survey, as posted on the TETR.IO Discord server

Many players in the community hold a very low opinion on TETR.IO's passthrough and, to a lesser degree, Multiplier mechanics. Previously, these mechanics would complement each other in creating unfair situations for both players; so much so, a large community-led discussion regarding the removal of the passthrough mechanic was held due to its prevalence in deciding ranked games. While concepts regarding passthrough's removal was always tossed about with nearly any server related to TETR.IO, the discussion, which led to passthrough's official removal, began in an official capacity on the 28th of September, 2021, in a Discord thread in the official TETR.IO server. Players were informed and instructed to leave feedback about a new, experimental toggle for passthrough, through the #news channel and ingame patchnotes alongside the 6.1.0 update. Thanks to this official push for opinions, the "Passthrough Removal" thread quickly became the second most active and popular one in TETR.IO's thread list with approximately 146 members today, leading only behind the "Official Character System Thread", which has about 195 users in it.

“Please only vote if you've actually played w/ passthrough disabled. I won't be looking so much at the raw vote counts, but rather at the reasons given. Please be sure to fill them out. Thank you for voting!”

—osk "#news". TETR.IO Discord server. October 17, 2021. Retrieved .

While discussion in the thread progressed semi-smoothly, it was necessary to attain an overview of players for and against the change. To solve this issue, osk would set up a site known as https://passthrough.osk.sh/. While the form is closed today, during the submission period, members were asked to fill out only 3 forms.

1. Are you for or against the removal of passthrough?
2. What is your TR? (if any)
3. "Please explain in detail why you have voted to keep/remove passthrough. This is the most important field!"

These questions would be answered by the community, amounting to a total of 649 entries, with duplicate or spam entries filtered out. Of those entries, 243 users voted to keep passthrough, and 406 users voted to remove it.

“After reading all 649 responses, I've decided to remove passthrough from TETRA LEAGUE and QUICK PLAY, and disable it by default in all custom games.
The main reasoning here being that passthrough generally makes defending harder in an already high-damage game, and most importantly, is far too unpredictable (even pure RNG would be more predictable).”

—osk "#news". TETR.IO Discord server. October 17, 2021. Retrieved .

While passthrough has been "removed", it is very important to note that passthrough was still possible after the update, due to networking delays. 6.3.3 completely rectified this phenomena, dubbed "lagthrough" by the community, with a feature known as Zero Passthrough.

Seasonal events

April Fools'

Like most of the internet, on April 1st each year, TETR.IO takes part in the April Fools' Day festivities usually by changing the system Quick Play room's ruleset to one that is both unconventional and impossible to recreate for the normal user, and by changing the so-called "action text" that appears when the player clears lines, T-Spins, All Clears, and Back-To-Back moves.

April Fools' 2020

Illustration of the so-called "Dark Garbage" this year's TETR.IO April Fools' Quick Play was centered around. All players would begin each Quick Play lobby with this field before the countdown even began.

The specific line this block was located on would not abide by the universal rule normally applied in TETR.IO; the line would fail to clear if the line was filled.

Of course, other lines would clear as normal, however, once garbage entered the board, you would not be able to clear it. This created a bias for simply countering pending garbage to ensure none entered your board.

The Quick Play gimmick for this year's April Fools' was one singular unclearable block, located on the first row in the third column, leaving that row unclearable. Since garbage is added into the board from the bottom, once players covered a column on row 1 with a regular piece, garbage which has entered that row would become unclearable by extension. Furthermore, the garbage multiplier was set to a staggering 9999x, garbage margin time started instantly, the "ALLOWED SPINS" setting permitted "STUPID SPINS", and your next queue was reduced from five pieces to four. The "GARBAGE CAP" setting was set to a limit of 1 garbage line allowed to enter the field per non-line clearing piece placed, so matches wouldn't end the instant you received that aforementioned multiplied garbage. The winning strategy here appeared to be building up a 4-Wide setup, abusing stupid spins to counter as much garbage as possible, and stalling your way to the end.

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The action text this year mirrored that of NullpoMino's action text:

Original action text	Replaced action text
SINGLE	ONE
DOUBLE	TWO
TRIPLE	THREE
QUAD	FOUR
x-SPIN	LARGE x-SPEEN
MINI T-SPIN	TINY T-SPEEN
ALL CLEAR	VERY NICE
BACK TO BACK( x$x$)	MANY TIMES( x$x$)
$x$ COMBO	(unchanged)

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The TETR.IO Discord server also changed its name and server icon to match that of the Jstris Discord server. For many, there would be two identical Jstris Discord servers in their server list as Jstris did not reply with the vice-versa action.

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Gameplay footage

• Doremy's "[TETR.IO] Quick Play #8: april fooled (01-04-2020)"

Notes

April Fools' 2021

Here is an example of each "fractured" piece used in the final Quick play, starting with the equivalent of the Z tetromino.

This would have been the L piece.

The O tetromino was not changed, although since the ASC table was in effect, O-WIST's were still possible. This proves the system was capable of simply generating the same pieces.

The S piece.

The I piece justified the name of "fractured" pieces for this round. Minos had no obligation to be entirely connected.

The J piece.

The T piece. This generated piece is also commonly known as the F pentomino.

Exactly one year after the previous quick play event, shenanigans began once again. This time around, default Quick Play settings were in effect, plus the addition of normal allspin, however instead of using guideline tetrominos, all players were served the same seven randomly generated pieces known as "fractured" pieces. These pieces could be anywhere from one mino to sixteen minos large. Each fractured piece correlated to one of the regular seven guideline tetrominos both visually in the next/hold queue and in the "x-WIST" action text. Due to the randomly generated nature of these pieces, the Super Rotation System kickset was not a good fit for this mode. Hence, the dynamic "ASC" kicktable, originally created for winterNebs' Ascension, made a good fit for the mode. The kick table might not have been the only bit of inspiration taken from that site for this mode. Ascension's "Mutation" mode generates very similar pieces on later mutation levels. Fortunately, the ASC kick table was already implemented into TETR.IO as of update 0.7.2-pre0 released the year prior, however, despite the groundwork already existing for the kick table, the ASC kick table does not define 180 kicks to be used, so custom modifications adding mentioned 180 kicks were made to the ASC kick table at the time for this special mode. The winning strategy here differed from round to round depending on how favorable the fractured pieces generated. More than likely, pieces would simply be too unorthodox to legitimately play the game with, so good knowledge of the lock delay mechanics went a long way towards stalling your way to the end.

---

The T-Wist in its first appearance.

The action text switches this time around took a more simplistic approach to displaying how many lines a single piece cleared:

Original action text	Replaced action text
SINGLE	(unchanged)
DOUBLE	SINGLE x2
TRIPLE	SINGLE x3
QUAD	SINGLE x4
PENTA, HEXA, HEPTA, etc	SINGLE x$x$
KAGARIS	KAGARIN IS CUTE
x-SPIN	x-WIST
MINI T-SPIN	MINI T-WIST
ALL CLEAR	BRAVO
B2B x$x$	CHAIN x$x$
$x$ COMBO	(unchanged)

The "T-WIST" text is likely a reference to GlitchyPSI's YouTube video titled "A casual day with a twist.". The "BRAVO" text likely drew inspiration from the Tetris The Grand Master series, where an "all clear" is called a "bravo" in earlier games. The "CHAIN" text could be a reference to the Puyo Puyo series, but there's a higher chance it simply references the name of the Back-To-Back Chaining mechanic.

---

The TETR.IO Discord server did their part in the tomfoolery by changing its name to a self-aware violation of the | branding guidelines by changing its name to "Tetr.IO". Furthermore, the moment the date hit April the 1st for the CEST time zone, the following announcement was made in #news parallel to the update that changed the Quick Play ruleset:

The "JSTRIS handling mode" toggle. Activating it would produce the visuals shown above.

“Version 6.0.4a is now live.
➔ Added JSTRIS handling mode!
　-> It makes your handling exactly like Jstris handling. Find it in CONFIG -> HANDLING
➔ I couldn't be bothered to write the rest of the patch notes sorry”

—osk

This "Jstris handling mode" manifested as a toggle in the handling category of the config. Activating it would remove the frame based indications of how DAS and ARR were configured, and would replace them with counters that tracked milliseconds, just like Jstris. Changing your ARR value would impact your DAS value, specifically adding your ARR to your DAS. TETR.IO DAS/ARR is not the same as Jstris DAS/ARR, and the update that "fixed" TETR.IO's DAS suggests this addition workaround for users with positive ARR. Aside from the visual changes mentioned, this toggle effectively did nothing to change TETR.IO's handling.

---

Gameplay footage

• Lilla Oshisaure's "TETR.IO with bad pieces" stream
• JG Zeem's "[Tetr.io] Tetra league JJ_ZEEM vs HARROMAN" video. If you needed proof that action text was globally changed, here it is. It didn't matter whether you played Zen mode or TETRA LEAGUE, a T-Spin was a T-Wist that day.
• Sretzo's "Tetr.io | Funny looking pieces (April Fool Super Lobby)" video

Notes

April Fools' 2022

Compared to the previous April Fools', 2022's foolery came and went to little official fanfare or acclaim. Lacking any external announcement over the server maintenance, aside from the standard ten minute timer ingame players are subject to, the event made up for this underwhelming aspect by lasting from March 31, 8:00 PM UTC to April 2, 12:00 PM UTC, a total of 40 hours. This subdued deployment was triggered in part by extended development time away from TETR.IO's main codebase, with development efforts going towards the still pending "Character System" update, which is set to release TETR.IO's beta; and by osk's unfavorable schedule at the time, which did not permit for extended debugging if launched at the normal times.

The extent of the April Fools' update, titled version "6.2.0a", applied only to the ingame QUICK PLAY room. No special action text was supplied, nor did any modification of the ingame CONFIG occur. QUICK PLAY's config was near-identical to non-April Fools' settings, bar usage of the ASC kick table and immobile allspin, with the addition of so-called "voids", "portals", or "voidholes". Every match, one to three voidholes materialized on the lower half of the matrix on each and every player board, randomized by seed. These indestructible, destructive objects are an unclearable nuisance; one that effects both your static field and your active piece. If either intersects a voidhole, be it by piloting an active piece into one or by accepting garbage and clearing lines, pushing the static field higher or lower respectively; the offending mino is destroyed.

• In the case of an active piece being partially destroyed, the piece remains controllable, however, should you continue to drive a piece into a voidhole, it will eventually be destroyed entirely.
  • Destroying a piece this way will still incur garbage accumulation, so as long as any opponent is still sending garbage, you cannot use this method to stall infinitely.
• In the case of your stack being pushed upwards into a voidhole, the voidhole will destroy all minos that would pass through it. The higher limit of three voidholes prevents scenarios where no garbage ever reaches the spawn position, as the maximum width of a spawning piece is four columns across.
  • Curiously, if the stack is pushed downwards two rows or more by a double line clear or higher, the voidhole will only consume the higher mino. This is theorized to be a simple oversight, as clearing rows below voidholes proves to be a difficult challenge while the voidholes themselves remain unclearable.

The simple fact of voidholes being unclearable makes this challenge similar to that of the first April Fools'. Unlike that event, however, the winning strategy here involved using your voidholes to attain trivial 1 row All Clears by partially destroying every piece into pseudo-monominos or pseudo-dominos during the opener phase, and then relying on efficient line clears for frequent countering, as well as an understanding of downstacking with L or J pieces above voidholes after receiving garbage. Good knowledge of ASC rotation under high gravity certainly heightened your chances of survival, since often times, players simply couldn't successfully navigate their pieces to where they needed to be under QUICK PLAY's quick endgame gravity.

Gameplay footage

• Wumbotize's "April Fools Day 2022 on Tetr.io" match
• Strode's Various Game's "April 1st, 2022 April Fools' Day Quick Play [TETR.IO]" stream archive
• Stepperステッパー's "April Fools Tetrio" video
• Edge's "How to WIN April Fools TETR.IO" clip
• am'bush' Gaming's "2022 April Fools' Quickplay is insane! | TETR.IO" extended gameplay

Notes

April Fools' 2023

2023 featured Kaliente mode, known initially as "?????" mode. The mode was made available site-wide for custom rooms and without any announcement or patchnotes at approximately March 31st, 11:50 PM UTC. Aside from the unique new game mode, action text and other configuration elements remained untouched. While Kaliente mode is enabled, the game over animation is much more explosive—whereas before the board simply fell, it now literally shatters into several pieces in a semi-3d effect while High or Ultra graphics are selected.

While initially planned to last the single day, Kaliente remained available for use in custom lobbies until 6.3.3's release about 11 days after April Fools'. After being removed from Quick Play following the April Fools' weekend, the tooltips associated with the options were revamped with helpful information pertaining to the mode.

The mode makes a couple differences immediately apparent. Before the game starts, players may notice that there is now a numerical HP value featured under their board. It transforms the winning condition into one where instead of being the last player to top out, you must be the last player with remaining HP. If you top out before your HP runs out, you will instead lose some amount of HP and continue playing, and your board will be partially cleared, leaving some difficult residue to clean up.

When players receive garbage, a specific column is highlighted a variable color to indicate that a "parry" may be made. When there is pending garbage, players may counter it by specifically clearing a row with an active piece partially above a parry point to perform a parry—where extra garbage is added to your line clear and sent to whoever you're targeting. In addition, parries may be "chained" off each other—for example, if a player parries an attack, it becomes a "double parry" which changes your board's color while pending. If parried again, a "triple parry", and so on. The more concurrent times a specific parry is passed around, the more damage it will do to your HP if any of its garbage is accepted. Players may forecast where this and future "parry points" will appear by studying the bottom of the field, where four differently colored arrows are present, pointing at specific columns. When a parry point is active, there will be a numerical value under it, signifying how many chained parries you are about to receive.

When parries are chained, players can deduce how dire a situation has become by gauging the board's color or the aforementioned numerical value. A small table is included below which indicates what parry you have received:

Concurrent parry number	Ingame name for parrying it	Associated color
#1	Parry!	Reddish pink
#2	Double Parry!	Cyan
#3	Triple Parry!	Orange
#4	Quad Parry!	Green
#5	Penta Parry!	Dark blue
#6	Hexa Parry!	Magenta
#7	Hepta Parry!	Very light cyan
#8	Octa Parry!	Very light cyan
#9	Ennea Parry!	Very light cyan
#10	Octa Parry!	Very light cyan
#$x$	$x$-Parry!	Very light cyan

Many arbitrary variables were made available for all players to change. Here's a table of the available options as well as the Quick Play defaults.

Option	Internal /set name	Default Quick Play value	Included modernized tooltip	Included April Fools' tooltip
Enable Kaliente	game.options.kaliente	ON	Enable the temporary Kaliente mode, where you parry garbage to lower your opponent's HP.	If enabled, your computer will blast. ← What?
Starting HP	game.options.kaliente_hp	750	The starting HP in Kaliente mode.	What? There was treasure. And it's right here. [I point to my heart.]
Multiplier	game.options.kaliente_multiplier	1	Global multiplier of all HP damage.	There! Go fetch!
Margin time	game.options.kaliente_margin	0	Time in frames after which the damage multiplier for Kaliente goes up.	↑Yoshino Powerhiko
Increase	game.options.kaliente_increase	0.0085	Amount with which the damage multiplier increases per second.	You're banned from the internet from now on.
Topout cost	game.options.kaliente_topout_cost	0.3	Index of how much HP a topout costs.	Shizuru is happily performing photosynthesis.
Punishment cost	game.options.kaliente_punishment_cost	1.5	Index of the HP cost of tanking lines with your piece in the parry line.	I doubt that makes any sense to you, but it doesn't make sense to me either so there's nothing I can do.
Garbage impact	game.options.kaliente_amt_cost	1	The amount of impact the size of an attack (in garbage) has on its HP damage.	The impact of garbage like me.
Parry power	game.options.kaliente_parry_impact	2.15	The power (as in, 𝑛^x where 𝑛=this setting and x=the parry power) of parrying to the damage.	If this was a story... would I be like a protagonist?

The winning strategy for Kaliente mode was not very clear-cut. In theory, players could benefit from predicting parry columns and actively engaging with the systems put forth, but in practice, players may have felt more inclined to farm large Back-To-Back chains and generically counter incoming garbage, thereby ensuring no damage entered their board. The very chaotic nature of Quick Play at the time made it hard to determine when and how much garbage one player may receive after a given point. Default settings were modified, such as a lower starting garbage multiplier and a larger frame of garbage travel time before garbage became active, but these settings, when combined with Kaliente's large starting HP pool, made Quick Play matches last a long time. Long matches mean matches that go into Garbage Margin Time, and at that point, more RNG entered consideration as all attacks hit very hard.

Gameplay footage

• ICLY's TETR.IO April Fools Quickplay Begineer's Gameplay match
• Wumbotize's It's April Fools Day 2023 on Tetr.io match
• Talon S.'s TETR.IO - Winning Quick Play During the April Fools' 2023 Event match
• am'bush' Gaming's 2023 April Fools' Quickplay is awesome! | TETR.IO stream
• LTS's TETR.IO APRIL FOOLS stream

Notes

April Fools' 2024

2024's event had no coordinal announcements and ran from March 31st, 10:00 PM UTC, and ended with the release of 6.4.4 on April 2nd, 3:00 PM UTC. Quick Play had an imlpementation of bomb garbage similarly to Tetris Battle, where garbage generates as solid lines with an exposed core in one column, shown as a stylized ☢️. Placing a piece directly on top of this exposed core would clear the row of garbage, as well as subsequent rows underneath with the same bomb column. This action counts as a line clear, and thus, preserves combo/Back-to-Back status. Bombs also follow change-on-attack generation, much unlike Tetris Battle. This allows for line clears and T-Spins beyond Quads to be scored. Extended line clears would send the following:

Line Clear	Garbage sent
Quad	4+B2B
Penta	5+B2B
Hexa	6+B2B
$x$ rows cleared	$x$+B2B
T-Spin Double	4+B2B
T-Spin Triple	6+B2B
T-Spin Quad	10+B2B
T-Spin Penta	12+B2B
T-Spin Hexa	14+B2B
$x$ rows cleared with a T-Spin	$2x+2$+B2B

All players were allowed to access this new garbage mode in custom rooms by running /set options.usebombs=1 in the chat as a host on April Fools'. Bombs were solidified as a room option in 6.4.4, making them a permanent addition. In addition to bombs, two new random bag types were introduced for use in custom rooms or solo custom games: 7+1-bag and 7+2-bag. These use the standard Random Generator method, with 1 or 2 extra arbitrary pieces shuffled into each bag. This change makes openers far less reliable, and in most cases, impossible to perform.

Notes

Holidays

Ingame image of TETR.IO during the holiday seasons.

“Christmas is almost here! The entire TETR.IO team would like to wish you Happy Holidays!
Please enjoy a slight reskin of the game to fit the mood! Also, Supporter gifts are 25% off! Could make a nice gift!”

—osk, December 19th, 2021

Following the trends of other services, TETR.IO also partakes in seasonal redecorating. So far, we can expect a full changeup of vanilla backgrounds, boards, accent colors, and skins with the addition of snowy particles, as we saw during the weeks of December 19, 2021 - January 4th, 2022. This slight reskin was also responsible for some interesting developments as far as the modularity of TETR.IO customization is concerned, being the first deployment of skin/ghost mix-n-matching and introducing entirely new textures to the internal "board.png" file, doubling its size, which was later ditched when the update was reverted.

“Happy holidays from the TETR.IO team!!! Please enjoy the festive spirit we've given the game again this year!
Feeling grinchy? You can disable the festive skin in Config this time around.”

—osk, December 21st, 2022

Returning for 2022, this year's holiday reskin was much more fundamental in altering TETR.IO's look and feel. With a new, animated queue which dynamically flipped between two frames depending on how quickly you were playing, the counters to the side of the board also shook slightly upon each update. Attacks were replaced with snowballs, and the grid showed as a checkerboard pattern. Since this update changed much more than last year's, Players were able to toggle it on and off via a setting posted at the very top of the config. The festivities lasted from the 21st of December, 2022, to the 8th of January, 2023.

“Happy holidays from the TETR.IO team! Please enjoy the festive spirit added to the game!
This time, there's something quite special courtesy of @doktorocelot , do turn up the volume!”

—@tetriogame, December 17th, 2023

Back again for 2023, major additions include newly remixed menu and Blitz songs, the accumulation of snow dynamically present on your board, and an omnipresent, configurable snowstorm in the menus. Assets previously made for 2022's celebration return, and most customizations can be disabled using the same toggle at the top of the config. This event began on the 17th of December, 2023, and continued until the 8th of January, 2024.

5,000,000 Blast

See also: TETR.IO Badges: 5,000,000 Blast

In celebration of TETR.IO reaching five million players, a temporary SOLO game mode released parallel to the occasion. This mode, subtitled "5,000,000 BLAST" ingame, would exist for exactly 2 weeks, the first of which held a competition for high scorers. All users who placed #1000th or higher would receive a special badge, as well as free durations of Supporter, TETR.IO's paid subscription.

---

An illustration of two line clears made during this event, in this special mode. The first Quad is a COOL!! line clear, as no recent line clears have been made on the rightmost column. The 2nd Quad is a REGRET line clear, as it repeats the first one to the column.

The mode itself was a race to simply attain 5,000,000 points or more as quickly as possible. Games would start with an extremely low score multiplier, and this hidden multiplier would silently increase exponentially as the game went on. Players did so while actively working around a system of "originality" which rewarded unique line clears to the session, and punished duplicate line clears. Internally, this system was represented by a sequence of "buckets", one for each of the 10 columns in a TETR.IO board, and one for every action listed in the score table above. That is to say, the following actions would be judged in combination with the row you do them in:

• Singles, Doubles, Triples, and Quads.
• T-Spins: both Mini T-Spins and full T-Spins were judged separately.
• T-Spins which do not clear lines also count as a separate action.
• All Clears: notably, these were judged strongly negatively if cleared. Specifically: after doing two All Clears, any more will impose an immediate, permanent deficit on your internal originality variable, decreasing it by 9.15 units. This, in turn, led players to recieving negative score, eventually going below 0 points so long as one continued this behavior.

“COOL!! if
・total originality increase this placement exceeded 4 + {amt of lines cleared}
・originality is now more than 8 (to prevent first move from always being COOL!!
REGRET if
・you lost originality in any way (by trying to take from a near-empty bucket, or by doing excessive PCs)”

—osk "5 Million Blast Research". TETR.IO Discord server. March 8, 2022. Retrieved .

This system was displayed to the player with the terms "COOL!!" and "REGRET" onscreen, borrowing heavily from the TGM series's section time call-outs. While these were helpful indicators to nudge players in the right direction and were overall beneficial to the mode's playability, they were not absolute indicators of optimal gameplay and were based upon somewhat arbitrary cutoffs. The top 1000 submissions in the leaderboard hovered near the 200-300 blocks placed statistic. As a time based mode, naturally, you would want to lower the amount of required pieces to get more done with less inputting, so, abusing COOL!! line clears was a must-have for the high ranking players.

Staff

TETR.IO staff members are users responsible for moderation and general upkeep of the game and its community. Their main responsibilities include reviewing reports, answering support tickets, and moderating the Discord server.

Staff members have access to the admin panel, which is the main interface for moderation actions. They also (in most cases) have access to the support ticket system, a role in the TETR.IO Discord server which grants them moderation permissions, and access to staff-only Discord channels.

Staff Roles

TETR.IO has four distinct staff roles with varying levels of access and responsibility. Staff roles automatically have access to most Supporter and Verified perks, access to a number of exclusive emotes, and the ability to take host of any in-game lobby.

Community Moderator

The community moderator role was introduced in May 2023. As the entry level staff role on TETR.IO, community moderators handle chat moderation and less involved administrative tasks. Community moderators have a blue name in chat.

Global Moderator

Global moderators are established TETR.IO staff members with extended responsibilities. Global moderators have the authority to handle all types of rule violations, and have a light pink name in chat.

Administrator

The administrator role is functionally similar to the moderator role, with extended permissions to perform certain bureaucratic tasks. Administrators have a hot pink name in chat.

Sysop

Users with the sysop role have full administrative control over TETR.IO. Notably, sysops are the only users with the power to promote new staff members or deploy code changes. This role is exclusively reserved for TETR.IO founder osk, who has a green name in chat.

Staff Members

Staff Member	Role	Title	Appointment
osk	Sysop	osk / TETR.IO Founder (Lead Producer)	Launch - Present
Dimentio	Administrator	TETR.IO Programmer & Administrator	August 2021 - Present
Dr Ocelot	Administrator	TETR.IO Audio & Music Designer, Programmer & Administrator	June 2022 - Present
Garbo	Administrator	TETR.IO Game Designer	November 2020 - Present
Matthew	Administrator	TETR.IO Administrator	Launch - Present
ZaptorZap	Administrator	TETR.IO Administrator	May 2021 - Present
Zudo	Administrator	TETR.IO Administrator	August 2021 - Present
flash	Global Moderator	TETR.IO Assisting Programmer & Global Moderator	Launch - Present
alcazar	Global Moderator	TETR.IO Global Moderator	Launch - Present
deep4amthoughts	Global Moderator	TETR.IO Global Moderator	May 2021 - Present
flowerpetal	Global Moderator	TETR.IO Global Moderator	May 2023 - Present
gebruikersnaam	Global Moderator	TETR.IO Global Moderator	Launch - Present
thugginator	Global Moderator	TETR.IO Global Moderator	Launch - Present
sketchedpurple	Global Moderator	TETR.IO Global Moderator	May 2023 - Present
Blink	Community Moderator	TETR.IO Community Moderator	May 2023 - Present
nook	Global Moderator (former)	TETR.IO Alumni	Launch - June 2022

Development

TETR.IO began its life in the INDEV stage on the 19th of February, 2019. This phase would have extremely closed testing, limited to only osk and his personal friends. Less than a year later, TETR.IO would enter the INFDEV stage on January 31, 2020, when access to the game was opened for testers on a per request basis. During the Infdev release, players were required to represent their IP address to osk via Discord DMs or E-Mails in order to test this version. A month and a half later, the game entered the public Alpha stage on March 22, 2020. This time, all players are free to create/log in to their accounts and play the game.

On May 22, 2020, a desktop client of TETR.IO was released. Aside from being able to open the game without a web browser, this version also touts increased performance, alongside Discord "Rich Presence" integration and more granular control over VSync.

Trivia

A quick graphic detailing all of the level tags available in TETR.IO.

• A player's "level badge" evolves into different shapes and colors every ten levels, starting from level 1. Furthermore, levels supposedly cap at level 5000, however, as no TETR.IO player has reached this level, this fact remains a myth.
  • The tetris bot ZZZTOJ hit the level 5000 cap on October 6, 2023, though there are no visible stats to verify the gold badge.
• If the "First To" value is higher than 2 in any given multiplayer Battle Royale with less than eight players, the scoreboard at the top of the screen will match the colors of the seven Tetrominos, displaying each player and their current amount of wins.
• If the user uses command "/kagari" in room chat, they will be greeted with a system message, only the user invoking the command can see, which contains "CMD: :kagari:". Same thing goes for the command "/maho", but with the system message saying "CMD: :maho:" instead.
• The "WASD" control scheme, one of three choices in the controls config, is a direct mirror of osk's personal controls; the same controls they thought up on the spot in Tetris Friends since they didn't quite like the default controls.
• Some aspects of TETR.IO's UI design are loosely based off the Bejeweled series. An example of this inspiration involves the Zen mode level up animation, which takes inspiration comes from Bejeweled 2 and Bejeweled 3's similarly named Zen mode. You can even draw comparisions down to the color schemes of the Solo mode selection screen to Bejeweled Twist; a game that also has a red "Blitz", turquoise "Zen", and yellow "Challenge"+"Classic" buttons.

An example of concurrent attacks.

• The damage number popups that appear when sending or blocking lines bear a resemblance to the ones from the video game Persona 5, developed by Atlus' P-Studio. Similarly, when chaining multiple line attacks in a row within a short time between attacks, the damage number will increase and become bigger in size. The stronger the line attacks, the bigger the damage number becomes. Similarly, in Persona 5, the damage number increases when landing multiple hits on an enemy with a ranged weapon.
  • Previously, the damage numbers were yellow when sending lines, and only showed an individual number of lines sent for every attack. A yellow spike counter on the left side of the board was also present when sending 10 or more lines in quick succession. As of version 6.1.0, as part of the preparations for the upcoming Character System, the spike counter was removed in favor of the Persona 5-styled damage numbers so that they act as the spike counter itself like they do currently.
• In the engine, it is theoretically possible to clear more than four lines with one piece. This can be done by creating a custom board layout with rows already filled, as line clears are only processed after a piece is dropped. At first, clearing more than four lines with one piece would softlock the game as it tried to find action text for an action that wasn't defined. However, starting with the 4.1.0 update released on the 16th of July, 2020, that issue was removed. In return, osk added in the following action text for when players clear more than four lines:

Lines cleared	Action text
5	PENTA
6	HEXA
7	HEPTA
8	OCTA
9	ENNEA
10	DECA
11	HENDECA
12	DODECA
13	TRIADECA
14	TESSARADECA
15	PENTEDECA
16	HEXADECA
17	HEPTADECA
18	OCTADECA
19	ENNEADECA
20	EICOSA
21+	KAGARIS

• Despite these normally impossible actions being recognized through action text, these line clears do not send any lines or count for any score. If you end up testing this yourself, ensure there are no all clear bonuses in play.

This image shows the various role colors in TETR.IO.

• As of version 6.0.1, achieving a higher TETR.IO Supporter tier will cause a player's name to show in a brighter shade of orange in game, assuming they have Supporter themself. Tier 1 is achieved after purchasing Supporter or receiving a gift, Tier 2 (★) is currently achieved after lifetime supporter contributions reach €20, Tier 3 (★★) is €80 and Tier 4 (★★★) is €250.
• An easter egg exists in the social panel. If you use the search bar to attempt to find a user who is not your friend, you will be greeted with a message containing "Couldn't find anyone like that." in place of search results. If you then search for "anyone like that" you'll be greeted with a different message. This loop continues for quite a bit:

Search query	Ingame response
anyone like that	Couldn't find anyone with that name.
anyone with that name	Couldn't find that person.
that person	Couldn't find the specified user.
the specified user	Couldn't find anyone in your friends list with that name.
anyone in your friends list with that name	Couldn't find who you are looking for.
who you are looking for	Couldn't find any user in your friends list who matches the specified search term.
any user in your friends list who matches the specified search term	...

• At this point, the error icon will switch from an innocent depection of Kagari to a more judgemental Kagari. Searching for "..." will result in the regular error message, "Couldn't find anyone like that."

A quick chart showing the various numerals used in ZEN mode.

• ZEN levels are usually accompanied by small symbols whenever shown. These symbols resolve into custom, expanded roman numerals.
  • When the maximum numeral is reached, the sixth 500,000 and onward simply repeats the symbol, breaking the standard. This is unlikely to occur anytime soon, however, as the user attributed with the most ZEN levels has yet to break even 20,000 levels.
    • Their username is BLB.
• Upon loading the game, TETR.IO runs a fully customized benchmark based on the type of rendering WebGL expects from your computer. The results of this test, known as the Feecof test, are then used to preselect a graphics preset according to the following chart:

Feecof score	Graphics preset
Under 300,000	LOW
Above 300,000 and below 600,000	MEDIUM
Above 600,000	HIGH
ABOVE 1,000,000 and with TETR.IO Desktop	ULTRA

• Since TETR.IO's conception, there have been several competitions for increasingly long activities. Here's where those records stand as of the 9th of June, 2022:
  • The longest TETR.IO 40 LINES run currently stands at 2 hours and 40 minutes. It was ran by user agar02.
    • Notably, TETR.IO refuses to parse ranked SOLO replays that take over 30 minutes to complete, so this run wasn't officially uploaded to servers, and YouTube/replay files account for the evidence. That said—there's little to no motivating factor to present fake runs of this sort.
  • The longest single persistent play-session was livestreamed over the course of 18 hours by Excadrill on Twitch. This play-session covered over 547 separate "free-for-all" matches, to preserve the drop-in/drop-out "playing with viewers" nature of his usual stream format. Regardless, during this period, no major breaks or periods of inactivity took place, and Excadrill won 114 matches total.
  • Ever since this statistic has been tracked, the longest explicitly recorded server uptime stands at just over 56½ days, covering the time gap between versions 6.2.1 and 6.3.0, although osk believes the real record stands above 2 months.

External links

• Official website
• Official Discord server
• Official X (Twitter) account
• Desktop client download page
• Issue tracker
• Release log