Raiders of the Lost Aisle II

18 August 2026

Z80GameIsometricOriginal

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The site already has one Raiders of the Lost Aisle — a Christmas Eve toy-department heist. This is a second, separately-built game under the same title and the same isometric-engine idea, with a different story: it's Bank Holiday Monday, the discount shelves are down to the last few tins, and legend has it Aisle 13 — sealed off since the Great Stocktake — still holds one final, impossibly cheap prize. Security guard Big Dave does not share your enthusiasm for bargains.

Raiders of the Lost Aisle II title screen: the game title in yellow, a bargain-hunt-adventure subtitle, Q A O P movement instructions, and press S to start — The title card. Same joke, different aisle.

The same dimetric trick, a second time

Both games place every object at a map position (x, y, height) and project it onto the screen with the same dimetric formula: screen X from the difference of the two ground axes, screen Y from their sum, minus height. Rooms here are an 8×8 (Aisle 7) and a 6×6 grid (Aisle 13, the lost one), each object a small box drawn as two stacked rectangles — a dark "base" at ground level and a bright "top" shifted up by its height — everything sorted back-to-front each frame by ground position so a shopper walks convincingly behind a shelving unit without any real 3D renderer involved.

Aisle 7: a blue isometric floor with yellow shelving units, a green checkout counter, a red guard sprite, and a cyan player sprite — Aisle 7 — shelving, a trolley, the checkout, and Big Dave on patrol.

Three bugs a screenshot caught that the test suite didn't

This game has its own headless test suite (test_raiders2.py, built the same way as the rest of this site's Z80 programs: boot it, drive it through real control flow via z80mini.py, assert on outcomes, render the screen to PNG). Every logic assertion passed well before the game actually looked right. Three separate bugs only showed up once the renders were actually opened and looked at:

The title screen was completely blank. The print routine read glyph data from the real Spectrum ROM's character set at $3D00 — which works fine on real hardware and in a full emulator, but z80mini.py is a from-scratch interpreter with no ROM image loaded at all, so every glyph read came back as zero. No crash, no failed assertion — a bare black screen. The fix was switching to this codebase's own bundled 8×8 font (fontdata.inc, the same one the other programs here use), which lives in the assembled program itself and doesn't depend on anything being loaded at a fixed ROM address.
The floor rendered as a barcode. Clearing the play area between rooms used a hand-rolled byte-fill loop that tested for "done" with dec bc / ld a,b / or c — which overwrites A with the remaining countdown value. The very first byte in each row wrote a correct zero; every byte after that wrote whatever was left of the countdown instead, producing a decaying stripe pattern of stale pixel garbage under the next room's freshly-drawn floor. This is the same bug class flagged elsewhere in this codebase — a routine silently clobbering A as a side effect of something that looks unrelated — just a fresh instance of it. The fix doesn't route the fill value through A at all: ld (hl),0 writes the constant directly, leaving A free for the loop's own bookkeeping.
The guard could ambush the player the instant protection ended. Not a rendering bug, but one only the full automated playthrough surfaced: getting caught grants a brief invulnerability window, but if the guard converged onto the player's exact tile during that window (it keeps moving throughout) and was still standing there the moment it expired, the very next frame caught the player again with no time to react. The fix holds the grace timer at 1 rather than letting it lapse while the guard is still camped on the player's own tile, so the countdown only actually runs once there's genuinely space to escape into.

Aisle 13, the lost aisle, showing a magenta floor, a shelving unit, and the player sprite — Aisle 13. Quiet, dusty, unguarded — the tin's right there.

Caught, and paid in full

Getting caught sends the shopper back to Aisle 7's entrance, drops the tin if they were carrying it, and starts that grace period. Reach the checkout with the tin in hand and the till rings up a win.

Aisle 7 with a red CAUGHT! BACK TO START message across the bottom of the screen — Big Dave, doing his one job.

Aisle 7 with a yellow PAID IN FULL - YOU WIN! message across the bottom of the screen — Paid in full.

Play it, or read the other one

raiders2.tap — ready to run in Fuse or any .tap-capable emulator. Q A O P move along the two isometric axes, S starts and restarts.
raiders2.asm — the full commented source. Build it yourself: pasmo --tapbas raiders2.asm raiders2.tap
test_raiders2.py — the headless test suite, including the guard-catch and invulnerability checks described above.
Or read the original Raiders of the Lost Aisle, the Christmas Eve toy-department version this one shares its engine idea with.