For each frame, a piece may fall 0 to N places. Every time a frame is advanced, the number of frames a piece has been active is compared against a calculation of how many rows the piece should have dropped in that number of frames, which is based on the velocity table. The fall-rate for a single piece is computed as a percentage of row fallen per-frame, 60 times per second. Gravity in Ketris is modeled as a positive integer, with 1 being the lowest amount of gravity, and 15 being the highest. To simulate pieces moving in the game board, there is a concept of “gravity”, where-by a piece has a certain fall rate based on the state of the game (i.e.: level, notably). Val clock = Clock () val game = Game ( clock ) val input = Input ( screen, game ) val graphics = Graphics ( screen, game ) var inputState = InputState. Today, this is simply baked into a very basic loop managed by the clock code: It follows a fairly standard “game loop” iteration:

The current project is actually quite simple.

Given these two motivations and the fact I’ve always liked Tetris, I got the crazy idea to try to build Tetris, for the command line, using Lanterna. In a previous life I spent a good bit of time in the gaming industry, and while I mostly focused on server infrastructure, there was a ton of unique and fun challenges in that space that I occasionally miss. Sometimes I also like to tinker with game programming.

That said, for long-standing applications running in a headless environment, there seemed to be a potential, however small, for this to be a useful library with which to have some experience. Generally speaking, if you’re going to build a terminal interface, using Java isn’t the first choice if only because of startup performance and initial resident memory use. I thought this was an interesting library, if a little hard to justify in normal use-cases. Background #Ī couple of years ago, I ran across Lanterna, which is a Curses-style library, built to run portably on the JVM. To make a Tetris clone for the terminal using Kotlin… on the JVM. Sometimes it’s fun to try a new challenge, and sometimes it is fun to mix a few challenges together.

Kotlin for each loop