NES MMMM logo display with shimmer palette animation using https://github.com/kassane/zig-mos-bootstrap

mmmm-logo.zig

//! NES MMMM logo display with shimmer palette animation.
const neslib = @import("neslib");

/// Nametable address for tile at column `col`, row `row` on nametable A ($2000).
fn ntadr(col: u8, row: u8) u16 {
    return 0x2000 | (@as(u16, row) << 5) | col;
}

/// 16×16 tile map for the mark, anchored at (logo_col, logo_row).
/// Generated from mmmm-mark.chr (CHR plane 0 only).
const logo_col: u8 = 11;
const logo_row: u8 = 8;
const logo: [16][16]u8 = .{
    .{ 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F },
    .{ 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F },
    .{ 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F },
    .{ 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F },
    .{ 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F },
    .{ 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F },
    .{ 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F },
    .{ 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F },
    .{ 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F },
    .{ 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F },
    .{ 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF },
    .{ 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF },
    .{ 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF },
    .{ 0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF },
    .{ 0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF },
    .{ 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF },
};

/// Shimmer sequence: palette slot 1 cycle (~8 frames each).
const shimmer: [8]u8 = .{ 0x19, 0x1A, 0x1A, 0x19, 0x19, 0x1A, 0x1A, 0x19 };

export fn main() callconv(.c) void {
    const bg_palette: [16]u8 = .{
        0x0f, 0x00, 0x27, 0x30,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
    };

    neslib.ppu_off();
    neslib.pal_bg(&bg_palette);

    for (logo, 0..) |row, ty| {
        const y: u8 = @intCast(ty);

        neslib.vram_adr(ntadr(logo_col, logo_row + y));
        neslib.vram_write(&row, 11);
    }

    neslib.ppu_on_all();

    var frame: u8 = 0;

    while (true) {
        neslib.ppu_wait_nmi();
        neslib.pal_col(1, shimmer[(frame >> 4) & 7]);
        frame +%= 1;
    }
}

Zig examples targeting MOS 6502 platforms via zig-mos-bootstrap and llvm-mos-sdk