A deep technical breakdown of Endbot, a 256-byte DOS demo presented at Revision 2026 by HellMood/Desire. The demo renders a robot sprite with progressive bullet damage, a growing explosion ring, a scrolling checkerboard landscape, and a MIDI soundtrack — all from a single .com file built with FASM. The writeup dissects every byte-saving trick used: the Rrrola multiply trick for X/Y decomposition without division, BP as a global clock register, `hlt` for frame sync at ~30 FPS, `xlat` for 1-byte palette lookup, `aam 9` as a 2-byte modulo, `btc` for accumulating sprite damage, `ret` to exit via DOS int 20h, and the clever dual-use of sprite pixel data as MIDI initialization bytes. DosBox-X with MPU-401/FluidSynth emulation is required for proper MIDI output.
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