A second, independently-built take on the same premise: a bargain hunter, a security guard called Big Dave, and a legendary discount tin sealed away in Aisle 13. Same isometric-engine idea as the original, a different story, and its own fresh set of bugs a screenshot caught that the test suite alone never would have.
Is it possible to build an isometric engine of the same real technique as Knight Lore and Head Over Heels on a 48K Spectrum, not a simplified imitation? Yes. Height-aware projection, painter's-algorithm depth sorting, and genuine masked sprite compositing, proven with a before/after screenshot of exactly the bug masking exists to fix.
A genuine isometric engine for the 48K Spectrum: three connected rooms, a patrolling security guard, a countdown clock, and one very important Christmas Eve toy. In the spirit of Knight Lore and The Great Escape, built and tested from scratch — including four real bugs a screenshot caught and a logic test never could.
A complete, original single-screen arcade game in 2.6KB of hand-assembled Z80: dodge six lanes of traffic on a bike, delivering food before your phone battery dies. Built and tested the way modern software is, not the way 1983 software was.