flowchart TD
  K["Read keys
ROM KEY-SCAN at 028E"] --> U
  U["Update 8 entities
IX walks B480"] --> C
  C["Cull to window
16KB → 672 B at B180"] --> B
  B["Stamp blocks far → near
into buffer at A000"] --> S
  S["Blit sprites masked
into the same buffer"] --> F
  F["LDIR buffer → screen
A000 → 4000, one shot"] --> K