.quick4-shell {
  border: 1px solid #d9e2ec;
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 28px;
  background: linear-gradient(145deg, #fdfefe 0%, #f3f7fb 100%);
  color: #0f172a;
  box-shadow: 0 10px 26px rgba(15, 23, 42, 0.12);
}

.quick4-header {
  margin-bottom: 16px;
}

.quick4-title {
  margin: 0 0 4px;
  font-size: 1.3rem;
}

.quick4-subtitle {
  margin: 0;
  color: #475569;
  font-size: 0.95rem;
}

.quick4-layout {
  display: grid;
  gap: 16px;
  grid-template-columns: 1fr;
  margin-bottom: 12px;
}

.quick4-board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  background: #f2f6fb;
  padding: 8px;
  border-radius: 10px;
  border: 1px solid #d8e2ef;
}

.quick4-cell {
  aspect-ratio: 1 / 1;
  border-radius: 8px;
  border: 1px solid #d5deea;
  background: #ffffff;
  color: #0f172a;
  font-size: 1.2rem;
  display: grid;
  place-items: center;
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease, transform 0.1s ease;
  user-select: none;
}

.quick4-cell.is-given {
  background: #eef2f8;
  border-color: #ccd7e5;
  color: #475569;
  cursor: default;
}

.quick4-cell.is-selected {
  border-color: #3b82f6;
  box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.35);
}

.quick4-cell.is-error {
  border-color: #f97373;
  background: #ffecec;
}

.quick4-controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  align-items: flex-start;
}

.quick4-keypad {
  display: grid;
  grid-template-columns: repeat(3, minmax(60px, 1fr));
  gap: 8px;
  flex: 1;
}

.quick4-keypad button {
  border: 1px solid #d5deea;
  background: #eef2f8;
  color: #0f172a;
  border-radius: 10px;
  padding: 10px 12px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.1s ease, border-color 0.15s ease, background 0.15s ease;
}

.quick4-keypad button:hover {
  border-color: #3b82f6;
  background: #e4ecfb;
}

.quick4-keypad button:active {
  transform: translateY(1px);
}

.quick4-keypad .ghost {
  background: #f8fafc;
  color: #475569;
  border-style: dashed;
}

.quick4-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 4px;
}

.quick4-actions button {
  border-radius: 10px;
  border: 1px solid #d5deea;
  background: #f8fafc;
  color: #0f172a;
  padding: 12px 16px;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 4px 10px rgba(15, 23, 42, 0.08);
  transition: transform 0.1s ease, border-color 0.15s ease, background 0.15s ease, box-shadow 0.15s ease;
}

.quick4-actions button:hover {
  border-color: #3b82f6;
  background: #e4ecfb;
  box-shadow: 0 6px 14px rgba(37, 99, 235, 0.16);
}

.quick4-actions button:active {
  transform: translateY(1px) scale(0.99);
}

.quick4-actions button[data-action="quick4-new"],
.quick4-actions button[data-action="quick4-check"] {
  background: #2563eb;
  border-color: #1d4ed8;
  color: #ffffff;
  box-shadow: 0 6px 14px rgba(37, 99, 235, 0.18);
}

.quick4-actions button[data-action="quick4-new"]:hover,
.quick4-actions button[data-action="quick4-check"]:hover {
  background: #1d4ed8;
  border-color: #1e40af;
}

.quick4-actions button[data-action="quick4-clear"] {
  background: #f8fafc;
  border-color: #cbd5e1;
  color: #0f172a;
}

.quick4-status {
  display: block;
  margin: 20px 0 0;
  padding-top: 6px;
  color: #475569;
  font-size: 0.95rem;
}

@media (min-width: 720px) {
  .quick4-layout {
    grid-template-columns: 1fr 1fr;
    align-items: start;
  }
}