C64doku

A Sudoku game for the Commodore 64, written in C64 BASIC V2.

Features

• Random puzzle generation (band/stack shuffle method — no backtracking, fast on real hardware)
• Three difficulty levels: Easy (41 given numbers), Medium (31), Hard (23)
• Rotationally symmetric clue removal (classic newspaper-style pattern)
• Rule-based solution checking (validates rows/cols/3x3 boxes, not a fixed-answer compare)
• Cursor-based entry

Controls

Key	Action
W/A/S/D or cursor keys	Move selection
1-9	Enter number
0	Clear cell
C	Check solution
R	Restart (clear entries, keep puzzle)
N	New puzzle (re-prompts difficulty)
Q	Quit

Running

Download the c64doku.prg file and run it in VICE or upload it to a real C64 or the C64 Ultimate.

Known limitations

• Clue removal is random, not solver-verified
• Puzzles may not have a unique solution