// Port the key art to a 1989 handheld: four greens, nothing else.
// Then make PRESS START blink, the way every title screen did.
let shades = ["#0F380F", "#306230", "#8BAC0F", "#9BBC0F"];
let bayer = [0, 8, 2, 10, 12, 4, 14, 6, 3, 11, 1, 9, 15, 7, 13, 5];
let w = ps.doc_width();
let h = ps.doc_height();

// Pass 1: read every pixel's brightness into a histogram, and note
// where the gold PRESS START letters and their shadow sit.
let lum = [];
let hist = [];
hist.pad(256, 0);
let label = [];
for y in 0..h {
    for x in 0..w {
        let hex = ps.pixel_get(x, y);
        let c = color_components(hex);
        let l = (c[0] * 299 + c[1] * 587 + c[2] * 114) / 1000;
        lum.push(l);
        hist[l] += 1;
        if y > h * 3 / 4 && (hex == "#FFD23C" || hex == "#3A0E2B") { label.push(y * w + x); }
    }
}

// Night art is mostly dark. Half rank (histogram equalization), half
// raw brightness: shadows open up and highlights still read.
let rank = [];
let total = 0;
for n in hist { total += n; rank.push(total); }
print(`equalized ${w * h} px over 256 levels`);

// Pass 2: map to 4 shades. A 4x4 ordered dither keeps the
// gradients from collapsing into flat blocks.
for y in 0..h {
    for x in 0..w {
        let l = lum[y * w + x];
        let v = (rank[l] * 47 / total + l * 47 / 255) / 2;
        let level = v / 16;
        if v % 16 > bayer[(y % 4) * 4 + x % 4] { level += 1; }
        ps.pixel_set(x, y, shades[level.min(3)]);
    }
}
print(`${w * h} px in 4 shades`);

// Frame 2 is a copy with the label painted out: each letter pixel
// takes the shade just above the label, in its own column.
let top = h;
for i in label { top = top.min(i / w); }
ps_timeline_duplicate_frame(0);
for i in label {
    let x = i % w;
    ps.pixel_set(x, i / w, ps.pixel_get(x, (top - 1).max(0)));
}
ps_timeline_set_fps(2);
ps_timeline_set_loop_mode("loop");
print(`PRESS START: ${label.len()} px, ${ps_timeline_frame_count()} frames at 2 fps`);