:root {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #182234;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent-color: #38bdf8;
  --accent-hover: #0284c7;
  --border-color: #334155;
  --font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-family);
  line-height: 1.5;
  min-height: 100vh;
}

header {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 1.25rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.logo-icon {
  font-size: 2rem;
}

.logo h1 {
  font-size: 1.5rem;
  font-weight: 700;
  background: linear-gradient(135deg, #38bdf8, #818cf8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

nav ul {
  display: flex;
  list-style: none;
  gap: 0.5rem;
}

nav button {
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-secondary);
  padding: 0.5rem 1rem;
  border-radius: 0.5rem;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s ease;
}

nav button:hover, nav button.active {
  background-color: var(--bg-card);
  color: var(--accent-color);
  border-color: var(--border-color);
}

main {
  padding: 2rem;
  max-width: 1400px;
  margin: 0 auto;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

.card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.card h2 {
  font-size: 1.25rem;
  margin-bottom: 1rem;
  color: var(--accent-color);
}

/* Periodic Table Styles */
.periodic-table-grid {
  display: grid;
  grid-template-columns: repeat(18, 1fr);
  gap: 6px;
  overflow-x: auto;
  padding: 1rem 0;
}

.element-cell {
  aspect-ratio: 1;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 0.375rem;
  padding: 0.25rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  cursor: pointer;
  transition: transform 0.15s ease, border-color 0.15s ease;
  min-width: 55px;
}

.element-cell:hover {
  transform: scale(1.1);
  z-index: 10;
  border-color: var(--accent-color);
}

.element-number {
  font-size: 0.65rem;
  color: var(--text-secondary);
}

.element-symbol {
  font-size: 1.1rem;
  font-weight: 700;
  text-align: center;
}

.element-name {
  font-size: 0.6rem;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  color: var(--text-secondary);
}

/* Category Colors */
.category-alkali-metal { border-left: 3px solid #ff6b6b; }
.category-alkaline-earth { border-left: 3px solid #feca57; }
.category-transition-metal { border-left: 3px solid #48dbfb; }
.category-post-transition { border-left: 3px solid #1dd1a1; }
.category-metalloid { border-left: 3px solid #ff9ff3; }
.category-reactive-nonmetal { border-left: 3px solid #54a0ff; }
.category-noble-gas { border-left: 3px solid #5f27cd; }
.category-lanthanide { border-left: 3px solid #ff9f43; }
.category-actinide { border-left: 3px solid #ee5253; }

/* Category Filter Legend */
.legend-container {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
  cursor: pointer;
}

.legend-color {
  width: 12px;
  height: 12px;
  border-radius: 3px;
}

/* Modal / Drawer */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.75);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
}

.modal-overlay.active {
  opacity: 1;
  pointer-events: auto;
}

.modal-content {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  width: 90%;
  max-width: 600px;
  padding: 1.5rem;
  position: relative;
  max-height: 85vh;
  overflow-y: auto;
}

.modal-close {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: none;
  border: none;
  color: var(--text-secondary);
  font-size: 1.5rem;
  cursor: pointer;
}

.form-group {
  margin-bottom: 1rem;
}

label {
  display: block;
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.375rem;
}

input, select, textarea {
  width: 100%;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 0.625rem 0.875rem;
  border-radius: 0.5rem;
  font-size: 0.95rem;
}

input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--accent-color);
}

.btn {
  background-color: var(--accent-color);
  color: #0f172a;
  border: none;
  padding: 0.625rem 1.25rem;
  border-radius: 0.5rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.2s;
}

.btn:hover {
  background-color: var(--accent-hover);
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
}

.badge {
  display: inline-block;
  padding: 0.25rem 0.5rem;
  border-radius: 0.25rem;
  font-size: 0.75rem;
  font-weight: 600;
  background-color: var(--border-color);
  color: var(--accent-color);
}

.table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1rem;
}

.table th, .table td {
  padding: 0.75rem;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

.table th {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border-color);
  margin-top: 3rem;
}