Most people have played Tetris in some form or other. It is one of the most-cloned games in existence. It’s existed in some form on everything that can play games, and even some things that shouldn’t. The majority of Tetris clones only bear a superficial similarity to the game that real fans have come to know, though. This happens for various reasons, I’m sure, but the primary one is definitely ignorance. The technical details of how current official games work are actually quite interesting—but if you’re just writing a Tetris clone for your programming class, you probably have no idea they even exist. That’s why I’m going to tell you.
A short disclaimer: Tetris folks that got here from my Facebook page can skip this blog, it’s nothing new to you. TGM nerds may not apply, I’m talking Guideline here. TGM deserves its own post anyway.
Thing the first: Randomizers
You’re new to the game. You’re struggling just to make the pieces fit snugly, and level 2 is looking awfully fast to you. Somehow—maybe you read the manual (hah!), or maybe a friend told you—you’ve learned about the mythical Tetris. Four lines at once? you’re thinking. Sounds risky! You go for it. After some frustrated attempts, you’ve got yourself a pile of blocks with exactly one hole, all lined up. You’re so excited! All you need now is that straight line….
The randomizer is responsible for choosing what piece you get next. In the oldest Tetris games the piece sequence was as random as possible, which is why you could experience droughts (where you just wouldn’t get that piece you wanted) or floods (where you would keep getting that piece you didn’t want). Various randomizers have been invented and used, but the one in common use today is called the bag randomizer. Imagine taking one of each piece, putting them in a bag, shaking it up, and dumping them out in a random order. Repeat this process as often as necessary. The bag randomizer makes sure you get one of each piece every 7 pieces. This makes things a lot less random, and much smoother. Not everybody likes this method best, but there is one thing that can’t be argued: by reducing the dependence on getting specific pieces, this randomizer enables a player to focus their attention on more interesting strategic choices (such as spins, which I cover later in this post).
Another thing the bag randomizer contributes to is open field setups. These are when you create a predefined pattern in order to achieve a specific result, and it fills the same role in competitive Tetris as opening books do in various board games such as Chess. They are a sort of ice-breaker, giving you something useful to do while you are waiting for the game proper to get going. Without a bag randomizer and the ability to rely on getting each piece regularly, such setups would be much riskier, and that would be a shame since some of them are quite complex, elegant, or even beautiful.
Thing the second: Kicks
Tetris lets you rotate pieces, obviously. What happens when a piece can’t rotate the way you want, though? This has been dealt with in various ways, and the answer that predominates today is called a kick. When a player tells a piece to rotate, but some part of the piece would be blocked if it was allowed to rotate, the game then tries to move the piece somewhere else to accomodate the rotation. There are multiple kick systems, but I’m only going to talk about one of them.
Super rotation system, or SRS, describes a specific set of behaviors used in modern Tetris games. It covers everything from piece color and how pieces enter the field to how they rotate and, most importantly, how they kick. It is a subject of some contention among Tetris nerds whether SRS is any good, but I won’t bore you with the details of that debate. This post is, after all, about what makes it interesting. SRS kicks are complicated to follow from a mathematical standpoint, but they’re pretty easy from a visual and intuitive standpoint. Pieces appear to pivot or swing around some point in space, and this allows you to get them into places you never would have been able to otherwise. SRS kicks are a big topic with heavy ties to multiplayer, so I won’t cover it in depth here. Suffice it to say that clearing a line by kicking a piece into position is valuable—either for points in single player modes or for attacks in versus modes. Putting a piece into a place it couldn’t get to by kicking is called a twist, while clearing lines with a twist is called a spin. In most modern Tetris games, the T piece is the only piece that gets rewarded for spins, but that is starting to change with some of the very newest releases as well as many fan games.
Thing the third: Lock delay
In old Tetris games, pieces would “lock” into place shortly after coming into contact with the floor. More accurately, they lock into place as soon as they try to move downward due to gravity and can’t. This is no longer the case. These days, when a piece encounters the floor, it waits a certain amount of time before locking into place no matter how fast it is falling. Moreover, rotating or moving the piece will reset this counter, enabling you to essentially juggle pieces in place for as long as you need. What is this nonsense?!—so you might think, at least. I certainly did at first! I came to realize, though, that lock delay adds more to the game than it detracts. Like the bag randomizer, and kick systems, it takes away some of the difficulty of getting things done, which leaves the focus on what to do rather than how. It goes hand-in-hand with kicks, enabling a player to perform complicated maneuvers that would be unthinkable in older games.
Lock delay also enables play to continue in extremely high gravity. (Gravity in Tetris is the speed that pieces fall once they have appeared at the top.) Games these days can work up to gravity so high that pieces begin at the bottom of the screen, and this is still playable thanks to the idea of lock delay. Some restrictions are put on lock delay in various games and game types, but that is a bit too detailed to get into just yet.
But wait, there’s more!
Actually, no. There’s lots to write about, but for now I’ll settle for introducing some folks to the basics. Well, the kind-of-basics. There are people out there who haven’t played a Tetris version that lets you rotate both directions. I don’t really need to explain that to anybody though. You press one button to rotate left, and a different button to rotate right. Easy! If you can’t wait until my next Tetris blog to learn all about everything (including how you’re not nearly as good as you might have thought you were), you can always head on over to Hard Drop or Tetris Concept and dig right in. If not, well, I’ll see you next time!