nescript/examples/prng_demo.ne

// PRNG demo — sprite positions driven by the runtime PRNG.
//
// Each frame draws four sprites at addresses pulled from the
// xorshift-style `rand8()` intrinsic, with an extra `rand16()`
// sample binned into a horizontal velocity. Exercises `rand8`,
// `rand16`, and `seed_rand` end-to-end.

game "PRNG Demo" {
    mapper: NROM
}

var seeded: u8 = 0

on frame {
    if seeded == 0 {
        // Pin the seed so the recording is deterministic. The
        // runtime forces bit 0 of the low byte high so a zero
        // seed doesn't stick the LFSR.
        seed_rand(0x1234)
        seeded = 1
    }

    // Four random sprites per frame. Each call pulls fresh
    // entropy from the shared PRNG state, so the positions
    // drift over time instead of staying fixed.
    var x1: u8 = rand8()
    var y1: u8 = rand8()
    draw Ball at: (x1, y1)

    var x2: u8 = rand8()
    var y2: u8 = rand8()
    draw Ball at: (x2, y2)

    // rand16() returns u16; truncate to u8 for the draw.
    var r: u16 = rand16()
    var x3: u8 = r as u8
    var y3: u8 = (r >> 8) as u8
    draw Ball at: (x3, y3)

    var x4: u8 = rand8()
    var y4: u8 = rand8()
    draw Ball at: (x4, y4)
}

start Main