56 lines
3.6 KiB
Markdown
56 lines
3.6 KiB
Markdown
# Space Taxi -- open items
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Things worth doing, not commitments. Started 2026-10-05, when Space Taxi
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moved out of JoeyLib's tree into this repository; JoeyLib's own list
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(library and platform work) stays in JoeyLib.
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- [ ] **The C64's flown-sprite warp.** The level-name intro animates its
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warp by cycling the colors of a static star field painted into
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screen RAM, on every target (stTitle.c, `starPaletteApply` in
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stRender.c). The C64 flies seven star sprites out along its rays
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instead. That version, carry-flag exact ($44F8/$4500/$450C/$4513/
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$467A, the star velocity tables back in genC64Data.py), is kept in
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`patches/spriteWarp.patch` for reference: it was made against the
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working tree of 2026-10-05 before the warp's layout and pacing were
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redone, so it no longer applies as it stands. Measured then, the
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sprite warp ran 16.6-17.0 fps on the IIgs against the palette's 29.2
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(the bar was 30); ST 29.2 against the palette's 23.3, Amiga PAL 12.3
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against 18.8/13.6, DOS ~29.9 both ways. On the IIgs the cost is
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per-call overhead in save-and-draw and restore (~1.75k and ~1.25k
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cycles a star), not bytes moved, so it becomes feasible with a leaner
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save/draw/restore path for small cels in JoeyLib.
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The ST's palette warp was slow for a LIBRARY reason, fixed in JoeyLib
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2026-10-06 with no game change: every jlPaletteSet made the ST HAL
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requantize its whole per-scanline palette table (3200 entries, ~38 ms
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of 8 MHz 68000 each, Hatari profiler); it now requantizes only the
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palette that changed. Warp on the ST, page flips per second inside the
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warp from a Hatari io_write trace (same method before and after):
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13.5 -> 53.6 fps; the title's logo 17.4 -> 20.7. (The 23.3 above
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predates the 2026-10-05 intro-pacing change; this method gives 13.5 on
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the tree just before the fix.) JoeyLib also gained an STe build, which
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Space Taxi gets with `make ste` (build/ste, STe and Mega STe only): the
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warp runs the same 53.6 on an STe and 56.8 on a Mega STe. Other ports'
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palette paths were not touched by this fix.
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- [ ] **Does $4523 really leave sprites 0-6 enabled?** The level-name setup
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($4523..$4665, stIntroEnter in stTitle.c) never clears the enable bits
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of sprites 0-6 on the C64, but the port does. Settle it from the
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disassembly (every $D015 write on the path into the intro), and check
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it in VICE if the bytes leave doubt. Dropped out of JoeyLib's TODO in
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the 2026-10-05 split; restored 2026-10-06.
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- [ ] **What the C64 gate cannot reach.** `tools/stsim/gate.sh c64` holds
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all 25 screens to the real game, but only along the attract demo's
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machinery: its table RNG ($446A; a real game reads the SID noise
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oscillator, which the port stands in for with an LCG), one cabbie, and
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whatever the searched streams happen to do. Two-to-four-cabbie turns,
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the bonus cab at $3.00, refuelling on a fuel pad ($6E23's pump half),
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a crash with an UP fare aboard and the shift's end are exercised by no
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ride (gcov over the 25 rides shows exactly what is reached; level A's
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ride covers the hatch exit, $6BFB).
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- [ ] **Ticks that overrun a frame.** When a tick's work does not fit in
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one frame (level V's row shift, the speech player), the C64 flushes
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its sprites mid-frame and a collision near the top of the screen
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reaches the read a tick late (MECHANICS.md). The port assumes every
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tick fits; modeling it needs the C64's cycle timing per tick. Seen
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only on a level-V ride whose cab hit the top border on a shift tick.
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