// Milestone checks (the ledger) and the sky roof line used for cooling.
// ---------- Ledger ----------
function checkLedger() {
  const done = id => ledger[id];
  const mark = id => { if (!ledger[id]) { ledger[id] = tick || 1; emit({ t: 'milestone', id }); } };
  if (stats.dug >= 15) mark('dig');
  if (seen[FIRE]) { mark('fire'); if (!player.lens) { player.lens = true; } }
  if (seen[BRICK] || seen[RBRICK] || seen[BARBR]) mark('brick');
  if (seen[CHARCOAL]) mark('charcoal');
  if (stats.grown > 0) mark('grow');
  if (seen[MCU]) mark('copper');
  if (stats.bars > 0) mark('bars');
  if (player.bitTier >= 1) mark('bit1');
  let anyPower = false, steamOn = false;
  for (const mm of machines) if (mm) { if ((mm.type === 'wheel' || mm.type === 'engine') && mm.out > 0.5) anyPower = true; if (mm.type === 'engine' && mm.out > 1) steamOn = true; }
  if (anyPower && !POWER_FREE) mark('power');
  if (stats.moved >= 300) mark('auto');
  if (seen[MGL] || seen[GLASS] || seen[CULLET]) { mark('glass'); player.flask = true; }
  if (steamOn && !POWER_FREE) mark('steam');
  if (seen[MFE]) mark('iron');
  if (player.bitTier >= 2) mark('bit2');
  if (seen[MST]) mark('steel');
  if (player.bitTier >= 3) mark('bit3');
  if (player.tankTier >= 1) mark('tank');
  if (depthU(bot.y) > 0.85) mark('deep');
  if (stats.sold > 0) mark('sale');
  if (ordersDone > 0) mark('order');
  if (seen[MBZ] || seen[MBS]) mark('alloy');
  if (seen[AGORE] || seen[AUORE] || seen[SILVER] || seen[GOLD]) mark('precious');
  if (debt <= 0) mark('claim');
  if (earned >= 50000) mark('rich1');
  if (earned >= 200000) mark('rich2');
  void done;
}

// Topmost non-air cell of each column: air above it can shed heat to the sky.
function updateRoof() {
  scanRoof(0, W);
  roofDirty.fill(0);
}
function updateDirtyRoof() {
  for (let cx = 0; cx < CW; cx++) {
    if (!roofDirty[cx]) continue;
    scanRoof(cx << 5, Math.min(W, (cx + 1) << 5));
    roofDirty[cx] = 0;
  }
}
function scanRoof(x0, x1) {
  for (let x = x0; x < x1; x++) {
    let y = 0;
    for (; y < H; y++) { const ph = PH[mat[y * W + x]]; if (ph === PH_SOLID || ph === PH_POWDER || ph === PH_LIQUID) break; }
    roofY[x] = y;
  }
}