#app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
}

/* ── Toolbar ─────────────────────────────────────────────── */
#toolbar {
  flex: 0 0 auto;
  height: var(--toolbar-height);
  background: var(--bg-1);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 12px;
  overflow-x: auto;
  overflow-y: hidden;
}

#toolbar .separator {
  width: 1px;
  height: 28px;
  background: var(--border);
  flex-shrink: 0;
}

/* ── Controls bar ─────────────────────────────────────────── */
#controls-bar {
  flex: 0 0 auto;
  height: var(--controls-height);
  background: var(--bg-1);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 12px;
  overflow-x: auto;
  overflow-y: hidden;
}

#controls-bar .separator {
  width: 1px;
  height: 28px;
  background: var(--border);
  flex-shrink: 0;
}

/* ── Main area ───────────────────────────────────────────── */
#main {
  flex: 1 1 0;
  display: flex;
  overflow: hidden;
}

/* ── Grid area ───────────────────────────────────────────── */
#grid-area {
  flex: 1 1 0;
  display: flex;
  overflow: hidden;
}

/* Fixed piano keys column */
#piano-keys-wrapper {
  flex: 0 0 var(--piano-width);
  overflow: hidden;
  background: var(--bg-1);
  border-right: 1px solid var(--border);
  /* Height is set to match lanes-scroll content height via JS */
}

/* Right scrolling column: all horizontal lanes */
#lanes-scroll {
  flex: 1 1 0;
  overflow-x: auto;
  overflow-y: hidden;
  display: flex;
  flex-direction: column;
}

/* Piano roll canvas stack */
#grid-canvas-container {
  flex: 1 1 0;       /* takes remaining vertical space */
  position: relative;
  overflow: hidden;
}

#grid-canvas-container canvas {
  position: absolute;
  top: 0;
  left: 0;
  display: block;
}

/* ── Lane rows (velocity, CC, glide, substep) ─────────────── */
.lane-row {
  flex: 0 0 auto;
  display: flex;
  align-items: stretch;
  border-top: 1px solid var(--border);
  position: relative;
}

.lane-row-label {
  position: sticky;
  left: 0;
  z-index: 5;
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: var(--piano-width);
  width: var(--piano-width);
  flex-shrink: 0;
  background: var(--bg-2);
  border-right: 1px solid var(--border);
  font-size: 9px;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.lane-row canvas {
  display: block;
  flex: 0 0 auto;
}

/* ── Step editor sidebar ──────────────────────────────────── */
#step-editor {
  position: fixed;
  right: 0;
  top: calc(var(--toolbar-height) + var(--controls-height));
  bottom: 0;
  width: 220px;
  background: var(--bg-1);
  border-left: 1px solid var(--border);
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  z-index: 100;
  transform: translateX(100%);
  transition: transform 0.2s ease;
}

#step-editor.open { transform: translateX(0); }

/* ── Randomize panel ─────────────────────────────────────── */
#randomize-panel {
  position: fixed;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%) scale(0.95);
  width: 360px;
  background: var(--bg-2);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 16px;
  z-index: 200;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.15s, transform 0.15s;
}

#randomize-panel.open {
  opacity: 1;
  pointer-events: all;
  transform: translate(-50%, -50%) scale(1);
}

#overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.55);
  z-index: 190;
}
#overlay.open { display: block; }

/* ── Shared control primitives ───────────────────────────── */
.ctrl-group {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.ctrl-group label { white-space: nowrap; }

/* Transport buttons */
.transport-btn {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  padding: 0;
  flex-shrink: 0;
}

.play-btn.active {
  background: var(--green-dim);
  border-color: var(--green);
  color: var(--green);
}