Castle

Castle: the knight jumps beside the great tower, a bat below him, a goblin on the battlements, gems and floating ledges around the tower; mountains and a town in the background, the panel shows hearts, gems 3 of 43, a minimap of the castle, time and score.
Up the great tower, past a bat, to the goblin on the battlements.

A platformer for the Macintosh 512K. A knight races along the castle walls to the flag on the highest tower - double jump, dash, goblins to stomp, bats to dodge, 43 gems, four layers of parallax scrolling and sampled sound.

Made for
Macintosh 512K (64K ROM), System 3.2
Written in
68000 assembler: 6,028 lines in 8 files
Size
19 KB of code, 76 KB of sampled sound, 42 KB of graphics and the level
Level
5,120 pixels long: 13 goblins, 11 bats, 43 gems, 6 checkpoints
Speed
up to 30 frames per second; movement is scaled by the frame time, so the game keeps its pace at the big towers
Built with
mac68k-asm and mac68k-disk
Year
2026
Runs on
Macintosh 512K, 512Ke or Plus; System 3.2 or later; 400K floppy
Play in the browser Download the disk

About Castle

A knight races along the walls of a castle to the flag on its highest tower, against the clock. On the way: goblins on the walkways and ledges, bats that swoop down when he comes close, moats, lifts and 43 gems.

  • Moves. Run, jump as high as the Space key is held, jump a second time in the air with a somersault, and dash: a short fast move that ignores gravity and knocks out any goblin or bat in the way. Stomping a goblin from above bounces the knight up again.
  • Hearts and checkpoints. A touch by a goblin or a bat, or a fall into a moat, costs one of three hearts. The knight starts again at the last checkpoint pennant he passed.
  • The race. The clock runs until the knight takes the flag; the best time stays on the title screen.

How it was made

Castle was written by Claude Code, Anthropic’s coding agent, with mac68k-asm, mac68k-disk and the Mini vMac emulator, in which it tested every step itself - frame times measured with the VIA timer, the sound recorded and compared with the samples.

Under the hood: four layers that scroll at their own speed (sky with drifting clouds and the sun, mountains, a town, and the castle in front), drawn into the hidden one of the 512K’s two screen buffers and shown with a page flip; the knight, goblins and bats with a white halo so that they stand out against the dithered background; and a sound mixer that plays two sampled effects at once in every vertical blank. The graphics and the sounds are made by Python scripts.

Controls

Key Action
A / D run left / right
Space jump; again in the air: double jump
S or Shift dash (also through goblins and bats)
P pause
Q quit to the Finder

Screenshots

Castle title screen: the word Castle in calligraphy above mountains, a town and the castle wall with a knight and a goblin; the panel shows the controls and PRESS SPACE TO START.
The title screen is the live scene, with the controls in the panel.
Castle: the knight runs along the castle wall towards a moat, a goblin behind him, gems above the houses of the town.
The first steps along the wall, towards the first moat.
Castle: the knight in mid-jump between three bats above the town, a checkpoint pennant and a goblin on the walkway below.
Bats swoop down when the knight comes close.
Castle: the castle wall with a long moat, no hearts left; the panel says THE CASTLE, SPACE: BACK TO THE GATE, THE CASTLE - R.I.P.
No hearts left - back to the gate.

Screenshots from Mini vMac at the real speed of the machine.

Download

castle.dsk : 400K MFS startup floppy "Castle" with System 3.2, Finder 5.3 and Castle; it boots straight into the game, the same disk as in the emulator.

Use it with a floppy emulator or a disk writer on a real Mac, or start it in Mini vMac or any other emulator of the first Macs.

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