var level_offsets = [
    // layer data
    {"name": "layer1", "bytes": 3, "offset": LAYER1_OFFSET = 0x2E000},
    {"name": "layer2", "bytes": 3, "offset": 0x2E600},
    {"name": "sprite", "bytes": 2, "offset": 0x2EC00},

    // secondary header data
    {"name": "header1", "bytes": 1, "offset": 0x2F000},
    {"name": "header2", "bytes": 1, "offset": 0x2F200},
    {"name": "header3", "bytes": 1, "offset": 0x2F400},
    {"name": "header4", "bytes": 1, "offset": 0x2F600},
];

function moveSublevel(to, fm, rom)
{
    // copy all of the level pointers
    for (var i = 0; i < level_offsets.length; ++i)
    {
        var o = level_offsets[i];

        var fmx = o.offset + fm * o.bytes;
        var tox = o.offset + to * o.bytes;

        rom.set(rom.slice(fmx, fmx + o.bytes), tox);
    }

    // copy the TEST level into the now-freed sublevel slot
    rom.set([0x00, 0x80, 0x06], LAYER1_OFFSET + 3 * fm);
}