half4 main(float2 coords) {
    half4 x = half4(1, 1, 1, 1);

    // Verify that break is allowed in a while loop.
    while (x.a == 1) {
        x.r -= 0.25;
        if (x.r <= 0) break;
    }

    // Verify that continue is allowed in a while loop.
    while (x.b > 0) {
        x.b -= 0.25;
        if (x.a == 1) continue; // should always happen
        x.g = 0;
    }

    // x contains green.
    return x;
}