.expr-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.55rem;
  position: relative;
  z-index: 1;
}

.tile {
  min-width: 3.2rem;
  height: 3.6rem;
  padding: 0 0.7rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.9rem;
  font-weight: 900;
  border-radius: 16px;
  background: linear-gradient(160deg, #ffffff, #e6ecff);
  color: #2d1b69;
  cursor: pointer;
  box-shadow:
    0 4px 0 rgba(0, 0, 0, 0.25),
    0 6px 14px rgba(0, 0, 0, 0.35);
  transition:
    transform 120ms cubic-bezier(0.34, 1.56, 0.64, 1),
    box-shadow 150ms ease,
    background 150ms ease;
  touch-action: none;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.6);
}

.tile:hover {
  transform: translateY(-3px);
}

.tile.selected {
  outline: 3px solid var(--accent2);
  outline-offset: 3px;
  box-shadow:
    0 4px 0 rgba(0, 0, 0, 0.25),
    0 0 22px var(--accent2);
  animation: tile-pulse 1s ease-in-out infinite;
}

@keyframes tile-pulse {
  0%,
  100% {
    transform: translateY(-3px) scale(1);
  }
  50% {
    transform: translateY(-3px) scale(1.05);
  }
}

.tile.dragging {
  z-index: 10;
  box-shadow:
    0 10px 26px rgba(0, 0, 0, 0.5),
    0 0 24px var(--accent);
  opacity: 0.95;
  transform: scale(1.1);
}

.tile-num {
  background: linear-gradient(160deg, #ffffff, #d6e4ff);
}

.tile-round {
  background: linear-gradient(160deg, #fff7d6, #ffd23f);
  color: #7a5200;
  box-shadow:
    0 4px 0 rgba(180, 130, 0, 0.4),
    0 0 22px rgba(255, 210, 63, 0.8);
  animation: round-glow 1.6s ease-in-out infinite;
}

@keyframes round-glow {
  0%,
  100% {
    box-shadow:
      0 4px 0 rgba(180, 130, 0, 0.4),
      0 0 18px rgba(255, 210, 63, 0.6);
  }
  50% {
    box-shadow:
      0 4px 0 rgba(180, 130, 0, 0.4),
      0 0 30px rgba(255, 210, 63, 1);
  }
}

.tile-op-add {
  background: linear-gradient(160deg, #6bb7ff, #2b6ff5);
  color: #fff;
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
  box-shadow:
    0 4px 0 rgba(20, 60, 140, 0.5),
    0 0 16px rgba(43, 111, 245, 0.6);
}

.tile-op-mul {
  background: linear-gradient(160deg, #ff6ba6, #f52b7a);
  color: #fff;
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
  box-shadow:
    0 4px 0 rgba(140, 20, 70, 0.5),
    0 0 16px rgba(245, 43, 122, 0.6);
}
.tile-op-sign {
  cursor: default;
  opacity: 0.95;
  box-shadow: none;
  background: transparent;
  color: var(--accent3);
  text-shadow: 0 0 8px rgba(255, 210, 63, 0.5);
}
.tile-op-sign:hover {
  transform: none;
}

.tile-paren {
  background: transparent;
  box-shadow: none;
  color: var(--accent2);
  min-width: 1.5rem;
  font-size: 2.2rem;
  text-shadow: 0 0 10px rgba(0, 229, 255, 0.5);
}
.tile-paren:hover {
  transform: none;
}

/* Radial menu */
.radial-layer {
  position: absolute;
  pointer-events: none;
  z-index: 20;
}

.radial-layer.visible {
  pointer-events: auto;
}

.radial {
  position: absolute;
  transform: translate(-50%, -110%);
  display: flex;
  gap: 0.45rem;
  background: var(--panel-solid);
  padding: 0.55rem;
  border-radius: 16px;
  border: 2px solid var(--accent2);
  box-shadow:
    var(--shadow),
    0 0 22px rgba(0, 229, 255, 0.4);
  animation: radial-pop 160ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes radial-pop {
  from {
    opacity: 0;
    transform: translate(-50%, -100%) scale(0.7);
  }
  to {
    opacity: 1;
    transform: translate(-50%, -110%) scale(1);
  }
}

.radial-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
  border: 2px solid rgba(255, 255, 255, 0.15);
  background: linear-gradient(160deg, var(--accent2), #009fb5);
  border-radius: 12px;
  padding: 0.55rem 0.65rem;
  cursor: pointer;
  min-width: 3.1rem;
  color: #06232a;
  transition:
    transform 100ms ease,
    filter 150ms ease;
}

.radial-btn:hover {
  filter: brightness(1.2);
  transform: translateY(-2px);
}

.radial-btn:active {
  transform: translateY(1px) scale(0.95);
}

.radial-glyph {
  font-size: 1.4rem;
}

.radial-label {
  font-size: 0.7rem;
  font-weight: 800;
  color: #06232a;
}

/* Split chooser */
.chooser-layer {
  position: absolute;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  background: rgba(10, 5, 30, 0.65);
  backdrop-filter: blur(4px);
  z-index: 30;
}

.chooser-layer.visible {
  display: flex;
}

.chooser-panel {
  background: var(--panel-solid);
  border: 2px solid var(--accent);
  border-radius: 20px;
  padding: 1.35rem;
  box-shadow:
    var(--shadow),
    0 0 30px rgba(255, 60, 175, 0.4);
  min-width: 290px;
  animation: radial-pop 180ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

.chooser-title {
  font-weight: 900;
  margin-bottom: 0.85rem;
  color: var(--accent3);
  font-size: 1.15rem;
  text-shadow: 0 0 10px rgba(255, 210, 63, 0.4);
}

.chooser-options {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 0.85rem;
}

.chooser-btn {
  font-size: 1.1rem;
  font-weight: 800;
  padding: 0.65rem 0.95rem;
  border-radius: 12px;
  border: 2px solid rgba(255, 255, 255, 0.18);
  background: linear-gradient(160deg, var(--accent4), #3fc82e);
  color: #06320a;
  cursor: pointer;
  transition:
    transform 100ms ease,
    filter 150ms ease;
}

.chooser-btn:hover {
  filter: brightness(1.15);
  transform: translateY(-2px);
}

.chooser-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

.chooser-custom {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  flex-wrap: wrap;
  margin-bottom: 0.85rem;
}

.chooser-input {
  width: 4rem;
  font-size: 1rem;
  padding: 0.4rem;
  border-radius: 8px;
  border: 2px solid var(--accent2);
  background: var(--panel);
  color: var(--ink);
}

.chooser-op {
  font-size: 1rem;
  padding: 0.4rem;
  border-radius: 8px;
  background: var(--panel);
  color: var(--ink);
  border: 2px solid var(--accent2);
}

.chooser-feedback {
  font-weight: 700;
}

.chooser-feedback.ok {
  color: var(--accent4);
}

.chooser-feedback.bad {
  color: #ff8080;
}
.chooser-slider {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 0.75rem;
  margin-bottom: 0.85rem;
}
.chooser-slider-preview {
  font-size: 1.4rem;
  font-weight: 900;
  text-align: center;
  color: var(--accent3);
  text-shadow: 0 0 10px rgba(255, 210, 63, 0.4);
}
.chooser-range {
  width: 100%;
  accent-color: var(--accent);
  cursor: pointer;
}

.chooser-cancel {
  border: none;
  background: none;
  color: var(--muted);
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 700;
}

@media (prefers-reduced-motion: reduce) {
  .tile.selected,
  .tile-round,
  .radial,
  .chooser-panel {
    animation: none !important;
  }
}