body {
  font-family: system-ui, sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f8fafc;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
}
header {
  text-align: center;
  margin-top: 20px;
  color: #334155;
}

.playground-container {
  display: flex;
  gap: 40px;
  margin-top: 30px;
  width: 95%;
  max-width: 1200px;
  align-items: flex-start;
}

/* Left Panel: Draggable Classes (Now a grid for better organization) */
.class-palette {
  flex: 1.5;
  background: white;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 10px;
  margin-bottom: 20px;
}

h3 {
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 16px;
  color: #475569;
  border-bottom: 2px solid #f1f5f9;
  padding-bottom: 5px;
}

.draggable-class {
  padding: 8px 10px;
  background: #f1f5f9;
  border-radius: 6px;
  border: 1px solid #cbd5e1;
  cursor: grab;
  font-family: "Courier New", Courier, monospace;
  font-size: 13px;
  font-weight: 600;
  color: #0f172a;
  transition: all 0.1s;
  text-align: center;
}
.draggable-class:hover {
  background: #e2e8f0;
  border-color: #94a3b8;
}
.draggable-class:active {
  cursor: grabbing;
  transform: scale(0.95);
}

/* Right Panel: Target Drop Zone */
.target-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  position: sticky;
  top: 40px;
}

#target-box {
  /* Base size and border, but NO hardcoded layout or colors! */
  width: 250px;
  min-height: 250px;
  border: 2px dashed #94a3b8;
  transition: all 0.3s ease;
  font-family: sans-serif;
}
#target-box.drag-over {
  background-color: #f1f5f9;
  border-color: #3b82f6;
  transform: scale(1.02);
}

.target-content {
  padding: 20px;
  pointer-events: none; /* So the text doesn't block the drop event */
}

.controls {
  margin-top: 20px;
  display: flex;
  gap: 10px;
}
button {
  padding: 10px 20px;
  cursor: pointer;
  border: none;
  border-radius: 6px;
  font-weight: bold;
  font-size: 14px;
  transition: 0.2s;
}
#reset-btn {
  background: #ef4444;
  color: white;
}
#reset-btn:hover {
  background: #dc2626;
}