Star Trip by Brainlez Coders!
# brainlez Coders! : startrip A 128 byte DOS intro written by pestis / bC!, submitted to the Lovebyte 2022 128b intro competition. Source code: https://github.com/vsariola/startrip Capture: https://youtu.be/Fd1mMbR2ulE Probably DOSBox only. This size category is just coder porn, normal people should not bother. Greets to superogue, HellMood, TomCat, baze, Ped7g, byteobserver, ttg, DevEd/AYCE, Dresdenboy, Kuemmel, Harekiet, unlord, DrClaw. ## Building You need [nasm](https://nasm.us/). Then: ``` nasm startrip.asm -fbin -o startrip.com ``` or just run the `build.bat`. ## Statistics - Init (IRQ, mode, palette): 27 bytes - MIDI initialization code & data: 17 bytes - Visuals: 46 bytes - Music player & syncer: 23 bytes - Song data: 15 bytes - **Total: 128 bytes** ## Technical - The music is just linear array of note numbers, with a single byte index changing every interrupt. However, as the interrupt is running at 18.2 Hz, a simple `dec byte [time]` would result in a very fast tempo. Instead, we do the equivalent of `add byte [time], 17`. The important property of 17 is that 15 * 17 = 255 = -1, so the net effect of 15 cycles is to decrease the time by one, while in between, the time is a large value outside the array. Since the array is last in the program, at least DOSBox guarantees values outside it are all zeros. - During initialization, we dump the whole code & data to MIDI port, with rep outsb. It setups the instruments and starts playing that low frequency bass. - The visuals are a run-of-the-mill raycaster, drawing heavily from [Essence 64b](https://www.pouet.net/prod.php?which=83204). The blinking "stars" are just a happy coincidence: the interrupt does not save/restore registers, so the raycaster calculations are screwed up every now and then. - The interrupt mutates the main code in two places: it decreases the Z to make the camera move forward with time. It also mutates the instruction that advances each ray in the inner loop of the raycaster: it puts the current note value there. Value of -1 means that no note is played. Value of -1 in the raycaster means the normal behaviour: each ray advances by one unit in Z every raycasting step. This glitches out the raycaster whenever we hit a note, giving the nice sync. Yes, this was totally found out by experimentation. - There is custom grayscale palette. Not sure if it was worth it. License: [MIT](LICENSE) 
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