// The tool hotbar and what is selected.
// ---------- HUD ----------
function renderHotbar() {
  const hb = $('hotbar'); hb.innerHTML = '';
  TOOLS.forEach((t, k) => {
    const b = el('button', { class: 'slot' + (k === GAME.tool ? ' on' : ''), title: `${t.name} (${t.key})`, 'aria-label': `${t.name} tool, key ${t.key}`, 'aria-pressed': k === GAME.tool });
    b.innerHTML = `<span class="k">${t.key}</span>${ICONS[t.id]}`;
    b.onclick = () => { selectTool(k); };
    hb.appendChild(b);
  });
}
function toolId() { return TOOLS[GAME.tool].id; }
// Shift does two jobs. While you are steering the bot it boosts; while you are not,
// it is the tool modifier (vacuum everything, fill a rectangle).
function steering() { return ['w', 'a', 's', 'd', 'ArrowUp', 'ArrowDown', 'ArrowLeft', 'ArrowRight', ' '].some(k => keys.has(k)) || GAME.padRun > 0; }
function modShift() { return keys.has('Shift') && !steering(); }
// The loose material exactly under the cursor, or the nearest one touching it.
function grainAt(ax, ay) {
  if (ax < 0 || ay < 0 || ax >= W || ay >= H) return 0;
  const i = ay * W + ax, m = mat[i];
  if (occ[i]) { const e = ents.find(e => ax >= e.ix && ax < e.ix + BAR_W && ay >= e.iy && ay < e.iy + BAR_H); if (e) return e.m; }
  if (PH[m] === PH_POWDER || (PH[m] === PH_LIQUID && player.flask)) return m;
  return vacuumTargetAt(ax, ay, 1);
}
function selectTool(k) {
  if (k === GAME.tool) return;
  GAME.tool = k; GAME.drag = null; hudDirty = true; renderHotbar(); playSfx('ui');
}
function bagMaterials() { return BAG_ORDER.filter(m => bag[m] > 0); }
function blowList() { return [...GAME.blow].filter(m => bag[m] > 0); }
// Shift + right click: an even mix of everything loose in the bag (bars never mix)
function blowAllList() { return bagMaterials().filter(m => PH[m] !== PH_ITEM && (PH[m] !== PH_LIQUID || player.flask)); }
function blowingAll() { return toolId() === 'vacuum' && (GAME.rmb ? !GAME.rmbConsumed && GAME.blowAll : modShift()); }
function piece() { return PIECES[GAME.pieceIdx]; }