Sound and the status LED: a small sequencer for the piezo.
CHGfx: a maximum-throughput ST7735 driver for the CHGame board (CH32X035G8U6 @ 48 MHz,...
The CHGame library's build switches.
The serial debug protocol (CHGAME_DEBUG builds only; see chgame/Config.h).
The house drawing: rounded rects and panels, span sprites (plain, scaled, flipped,...
Number formatting without printf.
Motion maths and the screen shake: easing, integer sine, randomness.
1 bpp scratch masks for outlined, shadowed and gradient lettering and logos.
The house palette: sixteen named colours, and the tricks a palette allows.
RAMFUNC(name): run a function from SRAM.
Saving: a record in flash that survives power cycles and re-uploads.