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 seven compiler bugs across the analyzer, IR lowerer, and codegen that were all fixed on the same branch (see git log for details).

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