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All posts for the month March, 2014

Tetris Rules

I’d meant to post about this a while ago, but lost the relevant link until now.

When I was in college, I wrote a tiny DOS Tetris clone called Blocks from Hell. I was an avid player of the game, and there were already many freeware and commercial clones around, but I was frustrated that they generally couldn’t keep up with really fast playing, and many of them seemed like they tried to change up aspects of the game, always to their detriment. My goal in writing my version was to make one that handled championship-level performance, and was as vanilla-standard as possible in its implementation of the game rules.

Well, the problem I ran into was that it wasn’t clear what “standard” meant regarding the rules of the game. I got my hands on every version and variant I could find (in 1989 or so), and they were kind of all over the map in their gameplay. Some things were mostly agreed-upon (like the size of the gameplay area and shapes of the blocks), but things like scoring and level advancement were clearly not. (For example, some of them gave a fixed score per piece played which didn’t reward the player for playing it early, while some of them did crazy things like have a maximum number of points that you could get for playing a piece, but subtracted from that every time the piece was moved or rotated, making it easy for an indecisive player to get no points.) Even things like how the pieces rotated varied among them.

Lacking an authoritative model, I set about trying all of them, and taking notes as to how they handled all of these game aspects. This meant playing random freeware Tetris games while mostly paying attention to the score, to reverse-engineer how some of them worked if they weren’t documented in that much detail. Armed with the information of the dozen-plus versions, I picked the aspects that seemed like the best-fit, or that felt like they made the most sense gameplay-wise. (In the case of the scoring, I went with a small fixed number of points per piece played, plus a bonus based on height from which the piece was dropped immediately down.) I was very pleased with the outcome, and it’s held up well enough that it’s still being played by some enthusiasts, 24 years later.

Well, a few years ago I ran across this article by Colin Fahey, which (along with a great history of the game) attempts to nail down an official set of gameplay rules for “Standard Tetris”, in part so that it could be more usefully used as an artificial intelligence arena. For this, Colin goes to the purest source — the pre-commercial DOS version of Tetris written by Alexey Pajitnov and Vadim Gerasimov in 1986, which I unfortunately never had the chance to test.

It turns out that I could have saved a lot of time if I had seen it, because it tracks almost perfectly with the choices that I used for Blocks from Hell. The scoring differs mostly because the original version didn’t reward the player for clearing lines(!), and the level advancement and speed control are basically identical, except the original starts at the equivalent of level 10 on Blocks.

Overall, I’m very pleased with how close to “pure” Tetris my efforts turned out to be, and I’m seriously impressed at how well-tuned the initial version by Pajitnov and Gerasimov was. Well, except for the lack of a line-clearing bonus. I just can’t get behind that.