Update 5-12-2013:

This article is getting pretty old by now, and there are some new things to know. Most useful of these is key bindings. You can configure your key bindings from your profile page; click the box you want, press the key, and click save when done. On a game page, your field must have the focus for the key presses to be caught. You can press ESC from anywhere on the page to scroll your field into view and focus it. There are also hotkeys for Commit (Ctrl+Enter) and Revert (Ctrl+Backspace).

What is King of Stackers?

King of Stackers is a turn-based Tetris game. Players take turns placing seven pieces until one player tops out. It sounds simple, but it's surprisingly fun - and an excellent way to learn both strategy and piece manipulation.

Getting started

The most useful page is the Activity section. It shows you the state of your active games and any challenges that are available to you. The Public Challenges section is where general challenges are shown. You are welcome to take these challenges too, but be aware that since they are open for anyone to take, some players will keep putting up new ones. Unless you want multiple games going with the same person, I suggest you only take a public challenge once :)

Related are the Challenges and the Games pages. The former allows you to review your outgoing challenges as well as any incoming ones, and issue new challenges. You can also issue challenges from a player's profile, which you can get to by clicking their name in the activity list or the member list.

The Chat section is there for you to say hi, ask questions, etc. The Memberlist page lets you see who has been playing recently and some stats about their performance. The Profile page shows your own profile. Note: You can set your key bindings through your profile page. The help page you've already found, and Logout does what it says.

The interface

By clicking View on a game in your Activity page, you will be taken to a game.

This is pretty straightforward too, but there are some things to say anyway. First and foremost, the game doesn't automatically update itself. This means if you happen to be playing when your opponent is taking turns, you will have to periodically hit Refresh (F5) to check if things have changed. Same applies to the chat.

The movement buttons do exactly what they say; Instant Drop is firm drop. Reset will reset a piece to its spawn orientation. Place Piece will drop the piece if necessary and lock it in place.

The Commit and Revert buttons are important to understand. The revert button will go back to the start of your turn, or the last point at which you committed your turn. Commit will move up your "save point" as well as reveal the full number of previews and your garbage holes. You can commit at any time during your turn. It is often advantageous to do so in order to make decisions about how to leave your field at the end of your turn.

There are a couple little status boxes that display certain important info. Jeopardy is how many lines you have pending in your garbage queue. Combo is where you are at in your combo. Back-to-Back shows whether your B2B bonus is enabled. In King of Stackers, attacks are received in first-in-last-out order. This is the opposite of what you are probably used to. You will need to read the chat log to see the amounts of the attacks; the last one you read will come first.

Game mechanics

King of Stackers uses the Super Rotation System in all game types. All spins are rewarded equally with +2 attack for every one line cleared in a spin. Spin detection is immobile. This means that a placement is considered a spin if the piece cannot move up, down, left, or right when you lock it. Some of the T-spins you know probably won't work, but other moves become available that you wouldn't be able to do with 3-point spin detection.

Combos and perfect clears are also rewarded. Garbage blocking and countering are present. Piece sequences and garbage sequences are not the same for both players. This is necessary since players alternate turns and can see each others' game states.

Randomizers - King of Stackers supports three randomizers:

Garbage types - King of Stackers supports five garbage types:

See the end of the document for detailed garbage information

Rotation

Rotation follows SRS kicks. There is a 180 rotate, but the kicks are nonfunctional except for the I, which has a sideways +3 or -3 kick in the horizontal positions.

Attack scoring

King of Stackers uses all-spins as follows:
If you place a piece and it cannot be moved up, down, left, or right without interference, it is considered a twist.
If a twisted piece clears any lines, it is a spin.
If the piece kicked, but did not clear every line it occupies, that spin is a mini. (For example, the T-spin triple kick but only two lines got cleared - part of the T is left behind)
Tetrises and spins activate the Back-to-Back bonus of +1 attack.
Triples send 2, doubles send 1. Triples, doubles, and singles will remove the B2B bonus.
Tetrises send 4 + B2B
Spins send 2*lines cleared + B2B
Mini spins send -1 attack
By default, perfect clears are exclusive (they don't stack with anything else), and send 8 lines.
The default combo table is: 0, 1, 1, 2, 2, 3, 3, 4, 4, 4...

The default game mode is Bag/Exclusive+, and this seems to be balanced pretty well.

Playing a game

For the next few sections, I am going to assume the game type is Bag/CoA.

The person who accepts a challenge gets the first turn. The first turn advantage is pretty effectively mitigated by Change on Attack, since any garbage you send can be used to return as much or more. The most garbage a player can send in one turn with a blank field is 5, but if you receive 4 clean garbage you can easily send back 9.

Most standard Tetris strategy applies in King of Stackers, but there are some specific things that don't apply in normal live games. Since KoS is turn-based and has no time limit, you can expect play to be extremely efficient. Between the lack of a time limit and All-spins, improvisation is king. Setting up complicated multiple-piece setups is not usually desirable, since relying on specific pieces makes you less efficient. Sorry, anyone who likes three-T openers.

Timing is also an important factor. In this context, timing means something a little different than usual. I'm referring to what you leave yourself at the end of your turn, and when you choose to attack, counter, or accept garbage. If you don't leave yourself any options for a downstack combo or some spins/attacks to block and counter garbage with, you are at the mercy of your opponent and you are giving up any chance of tactical decisions at the start of your next turn.

An average "good" attack in a turn could be 10, in the form of a Tetris and a spin double, so it's a good idea to have a spin double on hand to cut that down quite a bit - or better, a spin into downstack combo. You don't have to take it, but by having it prepared you will not only be able to decide after you've seen what your opponent did, but your preparedness will make your opponent a little more wary of going all-out and leaving themselves open.

Attacks of 13-16 are not unlikely at multiple points in a game with a good spinner, and under Change on Attack rules, more than that can crop up if you're unlucky (or your opponent is lucky!). The last bit of starter advice I have for you is to analyze your opponent's field before you play any pieces. Can they counter your attack? How much of it? If they accept your garbage, how much might they send back to you next turn? Don't get caught unawares if you expected them to counter but instead they took your garbage and sent you back 15.

Strategy

OK, so you're learning your spins, improvising attacks, keeping your options open, and in general getting a good feel for the game. But how do you win?

King of Stackers really brings out the beauty of the Change on Attack system. It's more important than ever to control what kind of garbage you send and what quantity you send. If you send your opponent lots of clean garbage, and he (or she!) has easy access to it, you can expect to see it come back to bite you for turns afterwards. Small combos, spin minis, and doubles are a great way to send your opponent some messy garbage. If they are in a bad situation one turn, that can be a great time to spike them with as much as you can send. Remember: if they can't clear any lines, they will have to accept the garbage.

A corrolary to this is: if the garbage would kill them, they will have to cancel it. This can force them to abort stronger attacks they had built, block themselves from accessing their garbage in a desperate attempt to combo down enough to stay alive, or spend attacks they could otherwise have spiked you with.

An interesting property of garbage canceling and Back-to-back is that if you send someone 5 clean garbage and they can cancel with a spin double or tetris - but don't have Back-to-back enabled - they will wind up with 1 messy garbage, which is all to the good.

It can be wise to review the attacks sent and let the messiness of the garbage factor into your decision about whether to cancel any or not. Accepting messy garbage can be a liability; if it builds up too much, you could have a hard time getting through it while remaining flexible enough to cancel attacks in the meantime. On the other hand, accepting clean garbage can be a real boon. If you ever run out of garbage, your attack power will be greatly diminished - and if your opponent isn't dead, they have a good chance of recovery. It is a good idea therefore to accept some clean garbage throughout the game when you have a good chance of reaching it and using it to your advantage.

If you are the one struggling to stay alive, try not to send any garbage to your opponent. It can be a rough time trying to stay alive but eventually they will exhaust their garbage and be unable to send you attacks that are as large. Tetrises, when you can utilize them, are especially effective for canceling - not only do they remove 4 (or 5) lines from your jeopardy, they also clear 4 lines from your screen - a net gain of 8 or 9 lines. Tetrises are hard to come by in a sticky situation though, so spin doubles are your next best bet.

Speaking of spin doubles, it's important to note that due to Back-to-back bonuses, spin singles are the most effective attack. They send 3:1 when B2B is enabled and their garbage is messier than the other options. It can be hard to maintain a steady string of singles, though, and spin doubles are the bread and butter of KoS play. Triples often require an entire turn to set up and are hardly worth it except in certain situations. They do store energy well, so that you can release a large attack or cancel a lot of garbage with one piece placement. They make effective attacks if you can form and execute them with very few pieces.

I touched on improvisation a bit above, but I'd like to address it in a little more detail here. In good play, you should never have to throw away pieces. You can spin 6 of the 7 pieces for attacks, so as long as you leave yourself options in your field shape, there should always be something you can do for an attack. Rather than build an attack and wait for the piece to execute it, you should aim to build an attack that will be executed with the piece that arrives when you complete the setup. If this isn't possible, then you should be using your extra pieces to create overhangs that can be used later (forecasting), or shore up your stack for a combo attack. Combos are generally not worth a lot unless they get up to around 7-combo because B2B is so valuable - but don't discount them for canceling garbage while clearing a mess, either!

Throughout the game there will be a lot of give and take, but it often falls out that the person who was about to lose stays alive long enough to get a nice downstack sequence - and that sequence can run you right out the top of your field. This is especially true with Change on Attack. If you are winning, you need to keep an eye out for opportunities to finish your opponent before your opponent can use your garbage against you. Since you are trying to keep up the pressure you will be sending lots of clean attacks - and if they survive long enough, eventually they'll have good options against you.

Pressuring them enough that they are forced to stack suboptimally, as mentioned above, is one good approach - they'll be hanging by their fingernails and if you can keep it up they'll fall eventually. If you wind up in that position, it can be a good idea to do everything you can to stay there.

Lucky downstacks can do it, too. When the Random Number God blesses you with just exactly the right piece sequence to stack from the top to the ground, the game can be over right then and there.

There's one last tip I can suggest, and that is building up a knockout punch. It is very tempting to keep pressuring as hard as you can when your opponent is on the verge of topping out, but players can be extremely tenacious in that situation, and chances aren't bad that they will eventually get back in the game. However, by spending one turn to build up rather than pressure, you can often accumulate all the added pressure you need to put them over the edge. This is very situational - you have to have the potential for a big spike, and they have to be in a position where one turn won't let them prepare enough or strike back very hard. You need to be prepared to accept garbage. If these things are true, then you can spend a whole turn stacking up an extra spin or two and release two turns' worth of attack in one - spiking them with just enough extra that they can't cancel enough in a turn to survive.

Opening setups

These can depend on whether you are going first or second. Perfect clear is a fairly decent general purpose opener, but it doesn't always succeed and sends a lot of clean garbage. You will have to clear lines with each of the last three pieces in order to succeed if your opponent sends you any lines after your first turn.

Spin singles and minis can get things going a little at a time - they aren't as likely to come right back to you in the form of a big attack, but they get things moving and send your opponent a little bit of a mess.

Spin doubles are easy to perform and can be an easy default, but have no particularly overwhelming merit. They send a free Tetris to your opponent, which is nigh guaranteed to come right back to you if you played first.

Most multiple T-spin setups aren't very helpful due to the reliance on getting T's, but TKI can be a good way to get things going as well.

In general, if you play first, you have to decide whether to build up a strong initial attack or to start pushing your opponent immediately. If you play second, you can react to your opponent's opening in whichever way is appropriate. I like to push hard if I notice my opponent going for a complicated setup that they can't complete since the garbage will be inaccessible for a little while. When playing first turn, I usually like to build a perfect clear and wait to see what my opponent does.

King of Stackers peculiarities

There are a number of these, and it is good to know about them. The first is the size and behavior of the field itself.

KoS uses a 10x25 matrix with 5 hidden rows at the top. Pieces spawn at the top of the hidden area, so even if your stack gets above the top in the middle of your screen, you may still be able to survive. The exception is the I piece, which spawns in row 24, allowing it to rotate from spawn without kicking. If dropping a piece will put your stack above where you can see, it is a good idea to memorize where you'd like to place your pieces - and with luck and a good grasp on SRS, you can often bring things back into sight.

Unlike some other games, you can lose a match in King of Stackers if any portion of your field goes above the top of the hidden area. This is unlike many games which have a very tall hidden area, or perhaps "cut off" the excess. This makes even center 4-wides risky: you can't let the edges of your field go up more than 5 above the top of the visible area.

180 kicks are pretty much nonexistent, but there are several uses for the 180 natural rotations. They allow L and J twists that might not otherwise exist, and they allow you to make certain L, J, S, and Z spins into full spins rather than minis that they might otherwise have been. Just remember that a natural rotation into a spin is a full spin, while a kick will be a mini if you don't clear all the lines.

Change on Attack garbage is also a little different. In most games, the first attack to be sent is the first one to be received. In King of Stackers, it is the reverse. If you send a Back-to-back Tetris and then a Double, and your opponent accepts it all, he will have a single hole on top and a line of five beneath it.

Detailed garbage information

Mode T-spin Other spin Perfect clear B2B Mini Combo table Notes
Exclusive+ 2 * lines 2 * lines attack = 8 +1 -1 0, 1, 1, 2, 3, 4, 3, 2, 2... Combos and spins do not stack. The greater of the two is used.
Change on Attack 2 * lines 2 * lines attack = 8 +1 -1 0, 1, 1, 2, 2, 3, 3, 4, 4, 4...
T-spin only 2 * lines - attack = 8 +1 -1 0, 1, 1, 2, 2, 3, 3, 4, 4, 4...
Air 2 1 * lines 1 * lines +4 +1 -1 1, 1, 1... Stack is pushed up, but no garbage is added underneath.
Slow 2 2 * lines 2 * lines attack = 8 +1 -1 0, 1, 1, 2, 2, 3, 3, 4, 4, 4... Attacks are accepted one at a time.
Classic - - - +1 - - No garbage countering, yes garbage blocking.