:root {
  --primary-bg: #f0f4f8;
  --surface-color: #ffffff;
  --text-main: #1f2937;
  --text-secondary: #4b5563;
  --accent-color: #3b82f6; /* Blue-500 */
  --accent-hover: #2563eb; /* Blue-600 */
  --correct-color: #10b981; /* Emerald-500 */
  --correct-bg: #d1fae5;
  --wrong-color: #ef4444; /* Red-500 */
  --wrong-bg: #fee2e2;
  --card-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --header-height: 80px;
}

body {
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background-color: var(--primary-bg);
  color: var(--text-main);
  height: 100vh;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

/* --- Layout --- */
.app-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1rem;
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

header {
  text-align: center;
  flex-shrink: 0;
}

h1 {
  font-size: 1.75rem;
  font-weight: 800;
  margin: 0 0 0.5rem 0;
  color: #111827;
  letter-spacing: -0.025em;
}

.controls {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
}

/* --- Buttons & Pills --- */
.btn {
  background-color: var(--text-main);
  color: white;
  border: none;
  padding: 0.5rem 1rem;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 0.5rem;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 0 1px 2px 0 rgba(0,0,0,0.05);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.btn:active {
  transform: translateY(0);
}

.btn.secondary {
  background-color: white;
  color: var(--text-main);
  border: 1px solid #d1d5db;
}

.btn.secondary:hover {
  background-color: #f9fafb;
  border-color: #9ca3af;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.pill {
  background: white;
  padding: 0.5rem 1rem;
  border-radius: 9999px;
  font-weight: 600;
  font-size: 0.95rem;
  border: 1px solid #e5e7eb;
  color: var(--text-secondary);
  box-shadow: 0 1px 2px 0 rgba(0,0,0,0.05);
  min-width: 120px;
  text-align: center;
}

/* --- Game Board --- */
.game-board {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  flex: 1;
  min-height: 0; /* Important for grid overflow */
}

.drop-zone {
  background: rgba(255, 255, 255, 0.7);
  backdrop-filter: blur(10px);
  border: 2px dashed #cbd5e1;
  border-radius: 1rem;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  transition: all 0.2s ease;
  position: relative;
  overflow: hidden;
}

.drop-zone.drag-over {
  background: rgba(239, 246, 255, 0.8);
  border-color: var(--accent-color);
  transform: scale(1.01);
}

.drop-zone h2 {
  margin: 0 0 1rem 0;
  text-align: center;
  font-size: 1.25rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  pointer-events: none;
}

.zone-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  overflow-y: auto;
  padding: 0.25rem;
}

/* --- Draggable Items --- */
.item {
  background: white;
  border: 1px solid #e5e7eb;
  padding: 1rem;
  border-radius: 0.75rem;
  font-weight: 700;
  text-align: center;
  cursor: grab;
  user-select: none;
  box-shadow: var(--card-shadow);
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.item:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  border-color: var(--accent-color);
}

.item:active {
  cursor: grabbing;
  transform: scale(0.95);
}

.item.correct {
  background-color: var(--correct-bg);
  color: #065f46;
  border-color: var(--correct-color);
  animation: popIn 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.item.wrong {
  background-color: var(--wrong-bg);
  color: #991b1b;
  border-color: var(--wrong-color);
  animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both;
}

/* Reduced size when in drop zone */
.zone-content .item {
  padding: 0.75rem;
  font-size: 1rem;
  margin: 0;
  box-shadow: 0 1px 3px 0 rgba(0,0,0,0.1);
}

/* --- Options Container --- */
.options-area {
  background: white;
  border-radius: 1rem 1rem 0 0;
  padding: 1.5rem;
  box-shadow: 0 -4px 6px -1px rgba(0, 0, 0, 0.05);
  z-index: 10;
  max-height: 35vh;
  overflow-y: auto;
}

.options-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  justify-content: center;
}

.options-grid .item {
  min-width: 150px;
  flex: 1 1 auto;
  max-width: 300px;
}

/* --- Feedback Message --- */
.feedback-msg {
  position: fixed;
  top: 1rem;
  left: 50%;
  transform: translateX(-50%) translateY(-150%);
  background: white;
  padding: 0.75rem 1.5rem;
  border-radius: 9999px;
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  font-weight: 600;
  z-index: 100;
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  border: 1px solid #e5e7eb;
}

.feedback-msg.visible {
  transform: translateX(-50%) translateY(0);
}

.feedback-msg.success { border-color: var(--correct-color); color: #065f46; }
.feedback-msg.error { border-color: var(--wrong-color); color: #991b1b; }

/* --- Footer --- */
footer {
  position: fixed;
  bottom: 0.5rem;
  right: 1rem;
  font-size: 0.75rem;
  color: #9ca3af;
  pointer-events: none;
}

/* --- Animations --- */
@keyframes shake {
  10%, 90% { transform: translate3d(-1px, 0, 0); }
  20%, 80% { transform: translate3d(2px, 0, 0); }
  30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
  40%, 60% { transform: translate3d(4px, 0, 0); }
}

@keyframes popIn {
  from { opacity: 0; transform: scale(0.8); }
  to { opacity: 1; transform: scale(1); }
}

/* --- Mobile --- */
@media (max-width: 768px) {
  h1 { font-size: 1.25rem; }
  .btn { padding: 0.4rem 0.8rem; font-size: 0.85rem; }
  .pill { padding: 0.4rem 0.8rem; font-size: 0.85rem; min-width: auto; }
  
  .game-board {
    grid-template-columns: 1fr;
    gap: 0.5rem;
  }
  
  .drop-zone {
    min-height: 150px;
  }
  
  .options-area {
    padding: 1rem;
  }
  
  .options-grid .item {
    padding: 0.75rem;
    font-size: 1rem;
    min-width: 100px;
  }
}