Struct ParticlePool 

pub struct ParticlePool<const N: usize> { /* private fields */ }

Fixed-capacity pool of N particles.

Uses a linear search for free slots on spawn. N up to ~128 is comfortably fast on a 33 MHz MIPS – if you’re routinely saturating a 256+ pool you want a proper object pool with a free-list, which lives at the engine layer.

Implementations

impl<const N: usize> ParticlePool<N>

pub const fn new() -> Self

A brand-new empty pool. Const-safe for static-array init.

pub fn spawn_burst( &mut self, rng: &mut LcgRng, centre: (i16, i16), color: (u8, u8, u8), count: usize, velocity_range: i16, ttl: u8, )

Spawn count particles at centre with velocities scattered within [-velocity_range, +velocity_range] on each axis (Q4.4). Colour and TTL are uniform across the burst.

Finds free slots via linear scan; if the pool is full the burst is truncated silently. Callers that care about guaranteed-spawns should size the pool to max_concurrent_bursts * count_per_burst.

rng is stepped for each spawned particle, seeding two signed values per axis.

pub fn update(&mut self, gravity: i16)

One simulation step for every live particle:

• Position += velocity (Q4.4: whole pixels move x, the remainder carries in x_frac to the next frame).
• vy += gravity (Q4.4, so 1 = 0.0625 px/frame² falling).
• ttl -= 1 – particle expires when it hits zero.

pub fn clear(&mut self)

Clear every slot. Use when resetting between levels so leftover particles don’t float in from the previous scene.

pub fn render_into_frame<'f, const OT_N: usize>( &self, frame: &mut OtFrame<'f, OT_N>, rects: &mut PrimitiveArena<'f, RectFlat>, z: u8, shake: (i16, i16), ) -> usize

Render every live particle as a RectFlat from rects into frame at slot z, stopping when the arena runs out. Returns the number of rects written.

Colour fades with ttl / spawn_ttl and size tapers from 3 px to 2 px.

pub fn live_count(&self) -> usize

How many slots currently hold live particles. O(N) scan – useful for debugging budgets + tests, not hot-path code.

pub fn particles(&self) -> &[Particle; N]

Immutable view of the raw particle array. Debugging helper; most consumers don’t need this.

Trait Implementations

impl<const N: usize> Default for ParticlePool<N>

fn default() -> Self

Returns the “default value” for a type.