nescript/examples

NEScript Examples

Quick Start

# Build the compiler
cargo build --release

# Compile all examples
for f in examples/*.ne; do cargo run -- build "$f"; done

# Or compile one
cargo run -- build examples/hello_sprite.ne

Open any .nes file in an NES emulator (Mesen, FCEUX, etc.)

Examples

File	Features	Description
hello_sprite.ne	input, draw	Move a sprite with the d-pad
bouncing_ball.ne	if/else, variables	Auto-bouncing sprite with edge detection
coin_cavern.ne	states, functions, constants	3-state game with gravity and coin collection
arrays_and_functions.ne	arrays, functions, while	Enemy array with collision detection
state_machine.ne	on enter/exit, transitions	Multi-state flow with timers
sprites_and_palettes.ne	sprites, scroll, cast	Inline CHR data, PPU scroll writes, type casting
mmc1_banked.ne	MMC1, banks, multiply	Banked mapper with software multiply
uxrom_user_banked.ne	UxROM, bank Foo { fun ... }, cross-bank trampoline	First example to put real user code inside a switchable bank. The animation step lives in bank Extras and is invoked from the fixed-bank state handler via a generated __tramp_step_animation stub that selects bank 0, JSRs the body, then restores the fixed bank before returning.
uxrom_banked_to_banked.ne	UxROM, banked → banked cross-bank call	Two bank Foo { fun ... } blocks: step lives in bank Logic and calls clamp in bank Helpers. The trampoline uses ZP_BANK_CURRENT + PHA/PLA to save and restore the caller's bank, so the same per-callee stub works whether the caller is in the fixed bank or another switchable bank.
palette_and_background.ne	palette, background, set_palette, load_background	Reset-time initial load plus vblank-safe runtime swaps
auto_chr_background.ne	background @nametable(...) with auto-CHR	First example to use the @nametable("file.png") shortcut without supplying any matching CHR data. The resolver dedupes the PNG's 8×8 cells, encodes them via the same brightness-bucketing the sprite CHR encoder uses, and slots them into CHR ROM at the next free tile slot. The committed auto_chr_bg.png is a 256×240 grayscale gradient that exercises ~50 unique tiles.
friendly_assets.ne	named colours, grouped palette, pixel art, tilemap+legend, palette_map, scalar sfx pitch, note-name music	Exercises every "friendlier" asset syntax at once — the palette uses bg0..sp3 + a shared universal:, the sprite is authored as ASCII pixel art, the background uses a legend { ... } + map: tilemap with a palette_map: for attributes, the sfx uses a scalar pitch: + envelope: alias, and the music uses note names (C4, E4 40, rest 10) with a tempo: default.
noise_triangle_sfx.ne	channel: noise, channel: triangle on sfx blocks	Demonstrates the noise and triangle sfx channels. Declares one noise burst and one triangle bass note, plays each on a timer so the emulator harness captures both the pixel output and the APU state.
sfx_pitch_envelope.ne	varying-pitch pulse SFX	A 16-frame frequency sweep written as a per-frame pitch: array on a Pulse-1 sfx. The compiler emits a separate __sfx_pitch_<name> blob and gates the audio tick's pitch update path on the __sfx_pitch_used marker, so programs that stick to the scalar pitch: form still get byte-identical ROM output.
metasprite_demo.ne	declarative multi-tile sprites	A 16×16 hero sprite split into a metasprite Hero { sprite: Hero16, dx: [...], dy: [...], frame: [...] } declaration. draw Hero at: (px, py) then expands to one DrawSprite op per tile in the IR lowering, each with its dx/dy added to the user's anchor point and the frame offset by the underlying sprite's base tile. The codegen needs no metasprite-specific support — it sees N regular draws and the OAM cursor allocator handles the slots.
nested_structs.ne	nested struct fields, array struct fields, chained literals	Two Hero instances each carry a Vec2 position and a u8[4] inventory. Exercises hero.pos.x chained access, hero.inv[i] array-field access, and chained struct-literal initializers (Hero { pos: Vec2 { x: ..., y: ... }, inv: [...] }).
platformer.ne	every subsystem	End-to-end side-scrolling demo: custom CHR tileset, full 32×30 nametable with per-region attribute palettes, 2×2 metasprite hero with gravity/jump physics, wrap-around horizontal scrolling, stomp-or-die enemy collisions with a live stomp-count HUD, coin pickups, user-declared SFX + music, and a Title → Playing → GameOver state machine with a proximity-based autopilot so the headless harness cycles through stomp, stomp, die, and retry inside six seconds. Regenerate the tile art with cargo run --bin gen_platformer_tiles.
sprite_flicker_demo.ne	cycle_sprites, 8-per-scanline hardware limit	Twelve sprites packed onto the same 4-pixel band — two more than the NES's 8-sprites-per-scanline hardware budget. The W0109 analyzer warning fires at compile time, and a cycle_sprites call at the end of on frame rotates the OAM DMA offset one slot per frame so the PPU drops a different sprite each frame. The permanent-dropout failure mode becomes visible flicker, which the eye reconstructs across frames. The classic NES technique used by Gradius, Battletoads, and every shmup that ever existed.
war.ne	production-quality card game, multi-file source layout	A complete port of the card game War, split across examples/war/*.ne files and pulled in via include directives. Title screen with a 0/1/2-player menu (cursor sprite, blinking PRESS A, brisk 4/4 march on pulse 2), a 50-frame deal animation, a deep Playing state with an inner phase machine (P_WAIT_A/P_FLY_A/.../P_WAR_BANNER/P_WAR_BURY/P_CHECK), card-conserving queue-based decks built on a 200-iteration random-swap shuffle, a "WAR!" tie-break that buries 3+1 face-down cards per player and plays a noise-channel thump per bury, and a victory screen with the builtin fanfare. The first NEScript example to use a top-level file as a thin shell that includes ~12 component files; building it surfaced and fixed two compiler bugs (E0506 too-many-params, and the IR-lowering wide_hi leak across functions). The remaining limitations and workarounds are catalogued in war/COMPILER_BUGS.md.

Emulator Controls

NES Button	Typical Key
D-pad	Arrow keys
A	Z
B	X
Start	Enter
Select	Right Shift

About Sprites

Sprite names in draw Player at: (x, y) are parsed and recorded in the AST. You can define sprites with inline CHR tile data:

sprite Player {
    chr: [0x3C, 0x42, 0x81, 0x81, 0x81, 0x81, 0x42, 0x3C,
          0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
}

If no matching sprite declaration exists, the draw uses the built-in default tile (a smiley face). See sprites_and_palettes.ne for a full example.

Compiler Commands

# Compile to ROM
cargo run -- build game.ne

# Custom output path
cargo run -- build game.ne --output my_game.nes

# Type-check only
cargo run -- check game.ne

# View generated 6502 assembly
cargo run -- build game.ne --asm-dump

# Debug mode
cargo run -- build game.ne --debug