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https://github.com/imjasonh/nescript
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platformer: sprite-based status bar with score + lives
Upgrades the platformer's "live coin count" into a proper heads-up
display that stays pinned to the top of the viewport while the
nametable scrolls. Left side: coin icon + two-digit stomp tally.
Right side: red heart icon + single-digit lives counter. Both ride
through the GameOver screen without jumping position, so the death
banner reads as a continuation of the same run.
Wire-up: three new cross-state bits — score now accumulates across
lives, `lives` starts at 3 and decrements in `GameOver.on_enter`,
and the GameOver → Playing retry bounces to Title instead when the
last heart is spent (Title's `on_enter` refills both).
Tile pipeline: ten decimal digits + a heart glyph added to the
committed Tileset (generator source in `scripts/gen_platformer_tiles.rs`
kept in sync). Digits use `c` (white) so they read against the
sky; the heart uses `a` (red) to match the cap/brick palette.
Division workaround: the obvious `stomp_count / 10` / `% 10` pair
miscompiles near state transitions — the built ROM cycles
Title → Playing → Title once per blink period with Playing
surviving exactly one frame. Swapping both calls for repeated
`while r >= 10 { r -= 10 }` helpers fixes it. Documented as a
new entry in `docs/future-work.md` so the next person reaching
for `/` or `%` knows to check there first.
Goldens, docs/platformer.gif, and the top-level + examples README
entries all refreshed in the same commit.
This commit is contained in:
Claude
parent
6b1cc98267
commit
b83b944570
9 changed files with 374 additions and 39 deletions
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@ -4,12 +4,17 @@
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// with per-region attribute palettes, a multi-tile metasprite
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// player with gravity/jump physics, wrap-around horizontal
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// scrolling, moving enemies with stomp-or-die contact logic, a
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// coin HUD that tracks live score, collectible coins, user-declared
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// SFX envelopes, a user-declared music track, and a
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// title → playing → game-over state machine driven by both
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// controller input and an autopilot so the jsnes golden harness
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// (which runs headless with no simulated buttons) still captures
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// the full gameplay loop inside the first ~6 seconds of demo.
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// sprite-based status bar at the top of the viewport (coin icon +
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// two-digit score on the left, heart icon + lives counter on the
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// right) that rides along through the death screen, cross-state
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// life tracking that cycles GameOver → Playing while hearts last
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// and bounces back to Title when the last heart is spent,
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// collectible coins, user-declared SFX envelopes, a user-declared
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// music track, and a title → playing → game-over state machine
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// driven by both controller input and an autopilot so the jsnes
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// golden harness (which runs headless with no simulated buttons)
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// still captures the full gameplay loop inside the first ~6
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// seconds of demo.
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//
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// Controls (when played by a human):
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// D-pad left/right — walk
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@ -212,6 +217,105 @@ sprite Tileset {
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"........",
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"........",
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"........",
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"........",
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// tile 16: Digit 0
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"........",
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"..cccc..",
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"..c..c..",
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"..c..c..",
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"..c..c..",
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"..c..c..",
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"..cccc..",
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"........",
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// tile 17: Digit 1
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"........",
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"...cc...",
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"..ccc...",
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"...cc...",
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"...cc...",
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"...cc...",
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"..cccc..",
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"........",
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// tile 18: Digit 2
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"........",
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"..cccc..",
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".....c..",
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"....cc..",
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"...cc...",
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"..cc....",
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"..cccc..",
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"........",
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// tile 19: Digit 3
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"........",
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"..cccc..",
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".....c..",
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"...ccc..",
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".....c..",
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".....c..",
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"..cccc..",
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"........",
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// tile 20: Digit 4
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"........",
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"..c..c..",
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"..c..c..",
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"..cccc..",
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".....c..",
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".....c..",
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".....c..",
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"........",
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// tile 21: Digit 5
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"........",
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"..cccc..",
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"..c.....",
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"..cccc..",
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".....c..",
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"..c..c..",
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"..cccc..",
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"........",
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// tile 22: Digit 6
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"........",
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"..cccc..",
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"..c.....",
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"..cccc..",
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"..c..c..",
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"..c..c..",
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"..cccc..",
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"........",
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// tile 23: Digit 7
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"........",
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"..cccc..",
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".....c..",
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"....c...",
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"...c....",
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"..c.....",
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"..c.....",
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"........",
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// tile 24: Digit 8
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"........",
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"..cccc..",
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"..c..c..",
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"..cccc..",
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"..c..c..",
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"..c..c..",
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"..cccc..",
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"........",
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// tile 25: Digit 9
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"........",
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"..cccc..",
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"..c..c..",
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"..cccc..",
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".....c..",
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".....c..",
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"..cccc..",
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"........",
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// tile 26: Heart
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"........",
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".aa..aa.",
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"aaaaaaaa",
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"aaaaaaaa",
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".aaaaaa.",
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"..aaaa..",
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"...aa...",
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"........"
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]
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}
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@ -223,6 +327,10 @@ const TILE_PLAYER_BL: u8 = 3
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const TILE_PLAYER_BR: u8 = 4
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const TILE_ENEMY: u8 = 5
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const TILE_COIN: u8 = 6
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// HUD glyphs (sprite-only — not referenced by the nametable). The
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// digit tiles are contiguous so `TILE_DIGIT_0 + n` picks digit `n`.
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const TILE_DIGIT_0: u8 = 16
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const TILE_HEART: u8 = 26
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// ── Background ──────────────────────────────────────────────
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// The 32×30 nametable is authored as ASCII art with a `legend`
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@ -378,6 +486,51 @@ const AUTOPILOT_JUMPS: u8 = 2
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// Cross-state scratch
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var frame_tick: u8 = 0 // free-running frame counter
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var stomp_count: u8 = 0 // successful enemy stomps this life
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var lives: u8 = 3 // lives remaining; HUD heart readout
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// ── HUD helpers ─────────────────────────────────────────────
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// Paint the four-sprite status bar at the very top of the screen:
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// a coin icon followed by a two-digit stomp tally on the left, and
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// a heart icon followed by a single-digit lives counter on the
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// right. Everything is drawn as OAM sprites (never the nametable)
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// so the HUD stays pinned while the background scrolls under it.
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// y = 16 is above the brick row, so the white digits read cleanly
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// against the universal-sky backdrop.
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// Split a 0..99 count into its tens and ones decimal digits via
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// repeated subtraction — the runtime's software divide has a known
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// issue that scribbles over state-local memory (tracked in
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// docs/future-work.md §G), and the HUD is hot enough that the
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// miscompile sends the state machine spinning. Manual repeated
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// subtraction is two dozen cycles for the worst case of a two-digit
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// score, which is cheap for a once-per-frame call.
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fun tens_digit(n: u8) -> u8 {
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var t: u8 = 0
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var r: u8 = n
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while r >= 10 {
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r -= 10
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t += 1
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}
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return t
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}
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fun ones_digit(n: u8) -> u8 {
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var r: u8 = n
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while r >= 10 {
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r -= 10
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}
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return r
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}
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fun draw_hud() {
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// Score side (left): coin + tens + ones.
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draw Tileset at: (16, 16) frame: TILE_COIN
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draw Tileset at: (28, 16) frame: TILE_DIGIT_0 + tens_digit(stomp_count)
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draw Tileset at: (36, 16) frame: TILE_DIGIT_0 + ones_digit(stomp_count)
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// Lives side (right): heart + digit.
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draw Tileset at: (208, 16) frame: TILE_HEART
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draw Tileset at: (224, 16) frame: TILE_DIGIT_0 + lives
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}
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// ── Helper functions ────────────────────────────────────────
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@ -486,6 +639,11 @@ state Title {
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on enter {
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blink = 0
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frame_tick = 0
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// Fresh run — restore the full life bar so the HUD reads 3
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// when Playing kicks in and the GameOver loop doesn't trap
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// the game in a zero-lives state forever.
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lives = 3
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stomp_count = 0
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start_music Theme
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}
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@ -628,21 +786,10 @@ state Playing {
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draw Tileset at: (c1_sx, cy) frame: TILE_COIN
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draw Tileset at: (c2_sx, COIN_Y) frame: TILE_COIN
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// Live HUD: draw one coin per stomp in the top-left. The
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// background palette-1 region covers this strip so the
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// sprite coins read correctly against the brick band.
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if stomp_count >= 1 {
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draw Tileset at: (16, 24) frame: TILE_COIN
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}
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if stomp_count >= 2 {
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draw Tileset at: (28, 24) frame: TILE_COIN
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}
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if stomp_count >= 3 {
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draw Tileset at: (40, 24) frame: TILE_COIN
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}
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if stomp_count >= 4 {
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draw Tileset at: (52, 24) frame: TILE_COIN
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}
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// Status bar (score tally on the left, lives on the right).
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// Drawn as sprites so it stays pinned while the nametable
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// scrolls under it.
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draw_hud()
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// Player is only drawn while alive — on the dying frame
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// we show the scene without the hero on top of the enemy
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@ -670,6 +817,12 @@ state GameOver {
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on enter {
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linger = 0
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// Burn a life on entry so the HUD's heart counter ticks
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// down visibly each death. Guard against underflow in case
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// something transitions here with lives already at zero.
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if lives > 0 {
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lives -= 1
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}
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stop_music
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}
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@ -686,26 +839,33 @@ state GameOver {
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draw Tileset at: (128, 112) frame: TILE_ENEMY
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draw Tileset at: (144, 112) frame: TILE_ENEMY
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if stomp_count >= 1 {
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draw Tileset at: (96, 128) frame: TILE_COIN
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}
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if stomp_count >= 2 {
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draw Tileset at: (112, 128) frame: TILE_COIN
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}
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if stomp_count >= 3 {
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draw Tileset at: (128, 128) frame: TILE_COIN
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}
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if stomp_count >= 4 {
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draw Tileset at: (144, 128) frame: TILE_COIN
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}
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// Carry the status bar through the death screen so the
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// final score and the remaining heart total are visible at
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// the exact same position as in Playing — no awkward jump.
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draw Tileset at: (16, 16) frame: TILE_COIN
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draw Tileset at: (28, 16) frame: TILE_DIGIT_0 + tens_digit(stomp_count)
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draw Tileset at: (36, 16) frame: TILE_DIGIT_0 + ones_digit(stomp_count)
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draw Tileset at: (208, 16) frame: TILE_HEART
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draw Tileset at: (224, 16) frame: TILE_DIGIT_0 + lives
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// Auto-retry after ~1 s so the headless harness sees the
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// full loop. A human can hit Start to retry immediately.
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// full loop. When the last life is spent, bounce back to
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// the Title screen instead (Title's `on enter` refills the
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// heart bar for the next run). A human can hit Start to
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// skip the wait.
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if linger >= 60 {
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transition Playing
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if lives == 0 {
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transition Title
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} else {
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transition Playing
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}
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}
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if button.start {
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transition Playing
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if lives == 0 {
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transition Title
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} else {
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transition Playing
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}
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}
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}
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}
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