Level
Transform cycle
Player
Time
Object queues
Score
Lives

Original controls: Z left, X right, ' up/jump, / down, RETURN yo-yo. Arrow keys are convenience aliases; Space aliases RETURN during play and starts from the title.

Other original-style controls: Q sound off, S sound on, Delete freeze, C continue, Escape return to title. Debug/navigation: 1/2/3 select A/B/C; [/] change transform.

Stage 4.13 scope: gameplay remains unchanged from the validated Stage 2.1/3 path. Sound now uses the BBC MOS pitch lookup, 100 Hz ENVELOPE state and SN76489 attenuation model, while Web Audio remains the final square-wave output. The attract screen runs the recovered 31-frame left/right transitions and final Trogg sequence. Title, cast and high-score text uses a fixed BBC 8×8 bitmap renderer. Stage 4.12 also restores the original screen-complete presentation: the gameplay raster is cleared, the BBC VDU-style “We've done it!” panel is drawn at its recovered coordinates, and only Trogg is animated walking off to the right. It retains the Stage 4.7 title-panel geometry, PrintPackedBCD-style score suppression, and final FRAK! bubble layering. Stage 4.12 also restores the original player-movement SOUND timing: the 100 Hz MOS envelope sub-ticks are scheduled 10 ms apart so the very short ENVELOPE 2 walking pulse is audible, with pitch taken from the pre-move Trogg Y coordinate exactly as in the 6502. The debug/control panel is hidden by default and can be toggled with Ctrl+D. Browsers require a user gesture before audio can become audible.