However, this process only works to rotate the shape in a single direction, it can't be used to do 180 degree rotation. This whole process makes rotating the blocks very simple in the code, and simple to represent. Here's how the T shaped tetromino goes: // using 0 for empty and 1 for filled, the T tetromino can be // represented in a 9 element array, where I've added wrapping // to make it easier to visualise 0 0 0 1 1 1 0 1 0 // which is the binary representation 0b000111010 = 58 // now applying an XOR operation we're able to flip bits 0b000111010 ^ 0b010100000 = 0b010011010 // and that binary, in a 3x3 square is 0 1 0 0 1 1 0 1 0 Let's look at how xor works: // 9 in binary is 1 0 0 1 // where a 1 appears, it will flip the bit in that position, // so the XOR operand we use is 1 0 1 0 // So 0b1001 (decimal 9) ^ (xor) 0b1010 (decimal 10) 1 0 0 1 ^ 1 0 1 0 - = 0 0 1 1 // decimal 3 // importantly the same XOR operand can be used to flip // 3 _back_ to 9: 0 0 1 1 ^ 1 0 1 0 - = 1 0 0 1 // decimal 9 If you have a value such as 9, in binary (prefixed with 0b) is 0b1001. It's useful to also understand how XOR operations work. I say simple, because it's a single operation against a single predetermined number. Using bitwise operations allows for a "simple" block rotation.
Remembering that my memory is stored as a linear array it means I'll store my representations of tetrominoes in the same way. In addition to the memory array, for debugging, I also copy the state of the memory into another array so I can page back and forwards through the current state of memory to ensure game play worked as I intended. fill method: const ROWS = 20 const COLS = 10 const memory = new Uint8Array ( ROWS * COLS ) const reset = ( ) => memory. In my typed array, I can choose to either store 0 and 1 for available and unavailable, or I could use the numeric value of the block letter (tetrominoes are named as T, L, J, S, Z, O).Įither way, initialising memory is simple and in fact resetting the game benefits from the. As the blocks themselves can be represented by a single value a typed array is a good fit. Since the game is so clearly defined as a 10x20 it made sense to quickly move to representing memory in an array of some sort. This didn't scale at all and quickly became a headache. The game itself plays out on an HTML5 canvas (which I believe to the best suited tech for this particular job) but in my Twitch coding attempt I tried to detect collision from the canvas itself (when the block bumps into a used pixel). From this, I was able to extract details I wanted about game play, block rotation, block selection and the random function used and timings.
#ALL TETRIS BLOCKS CODE#
Thankfully, someone has painstakingly disassembled the NES cartridge code and documented exactly how Tetris worked so that they could build a Tetris AI. I wanted the old school original game play (again, since it was all I had ever played). There's a wiki for Tetris gaming, but it's mostly based on the official guidelines that The Tetris Company (TTC) itself has published, and these are based on the 2001 (and onward) version of Tetris - which I didn't want. After the twitch session was over, I decided some reading would be useful to get a clear idea of how the blocks rotated, what the timing increases were (as the speed increases on each block of 10 rows cleared) and various other insights. Originally I decided to just eyeball how Tetris worked and replicated what I remembered from playing the Gameboy version when I was a kid. I've published 38 videos for new developers, designers, UX, UI, product owners and anyone who needs to conquer the command line today.
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