:root {
    --bg-primary: #0f1923;
    --bg-secondary: #1a2735;
    --bg-card: #1e3044;
    --bg-hover: #264060;
    --text-primary: #e8edf2;
    --text-secondary: #8fa3b8;
    --accent: #4fc3f7;
    --accent-hover: #29b6f6;
    --border: #2a4058;
    --success: #66bb6a;
    --warning: #ffa726;
    --danger: #ef5350;

    --cat-nonmetal: #4caf50;
    --cat-noble: #9c27b0;
    --cat-alkali: #f44336;
    --cat-alkaline: #ff9800;
    --cat-transition: #2196f3;
    --cat-post-transition: #607d8b;
    --cat-metalloid: #009688;
    --cat-halogen: #00bcd4;
    --cat-lanthanide: #e91e63;
    --cat-actinide: #ff5722;
    --cat-unknown: #78909c;
}

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

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
}

a {
    color: var(--accent);
    text-decoration: none;
    transition: color 0.2s;
}

a:hover {
    color: var(--accent-hover);
}

.navbar {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    padding: 0.75rem 1.5rem;
    display: flex;
    align-items: center;
    gap: 2rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.navbar .logo {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--accent);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    white-space: nowrap;
}

.navbar .logo .atom-icon {
    font-size: 1.5rem;
}

.nav-links {
    display: flex;
    gap: 0.25rem;
    flex-wrap: wrap;
}

.nav-links a {
    color: var(--text-secondary);
    padding: 0.4rem 0.75rem;
    border-radius: 6px;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.nav-links a:hover, .nav-links a.active {
    color: var(--text-primary);
    background: var(--bg-hover);
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1.5rem;
}

h1 {
    font-size: 1.8rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

h2 {
    font-size: 1.3rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.search-bar {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.search-bar input[type="text"],
.search-bar select {
    padding: 0.6rem 1rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.95rem;
    outline: none;
    transition: border-color 0.2s;
}

.search-bar input[type="text"]:focus,
.search-bar select:focus {
    border-color: var(--accent);
}

.search-bar input[type="text"] {
    flex: 1;
    min-width: 200px;
}

.btn {
    padding: 0.6rem 1.2rem;
    border: none;
    border-radius: 8px;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
    font-weight: 500;
}

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

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

.btn-secondary {
    background: var(--bg-hover);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    background: var(--border);
}

.btn-danger {
    background: var(--danger);
    color: white;
}

.btn-success {
    background: var(--success);
    color: white;
}

.btn-sm {
    padding: 0.35rem 0.75rem;
    font-size: 0.8rem;
}

.elements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
    gap: 0.75rem;
    margin-top: 1rem;
}

.element-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 1rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
}

.element-card:hover {
    transform: translateY(-3px);
    border-color: var(--accent);
    box-shadow: 0 4px 20px rgba(79, 195, 247, 0.15);
}

.element-card .number {
    font-size: 0.7rem;
    color: var(--text-secondary);
    position: absolute;
    top: 0.5rem;
    left: 0.5rem;
}

.element-card .symbol {
    font-size: 1.8rem;
    font-weight: 700;
    margin: 0.5rem 0 0.25rem;
}

.element-card .name {
    font-size: 0.75rem;
    color: var(--text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.element-card .mass {
    font-size: 0.65rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.element-card.nonmetal { border-left: 3px solid var(--cat-nonmetal); }
.element-card.noble-gas { border-left: 3px solid var(--cat-noble); }
.element-card.alkali-metal { border-left: 3px solid var(--cat-alkali); }
.element-card.alkaline-earth-metal { border-left: 3px solid var(--cat-alkaline); }
.element-card.transition-metal { border-left: 3px solid var(--cat-transition); }
.element-card.post-transition-metal { border-left: 3px solid var(--cat-post-transition); }
.element-card.metalloid { border-left: 3px solid var(--cat-metalloid); }
.element-card.halogen { border-left: 3px solid var(--cat-halogen); }
.element-card.lanthanide { border-left: 3px solid var(--cat-lanthanide); }
.element-card.actinide { border-left: 3px solid var(--cat-actinide); }
.element-card.unknown { border-left: 3px solid var(--cat-unknown); }

.legend {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    margin: 1rem 0;
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: 10px;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.legend-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
}

.detail-header {
    display: flex;
    align-items: flex-start;
    gap: 2rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.detail-symbol-box {
    background: var(--bg-card);
    border: 2px solid var(--border);
    border-radius: 16px;
    padding: 2rem;
    text-align: center;
    min-width: 160px;
}

.detail-symbol-box .symbol {
    font-size: 4rem;
    font-weight: 700;
    color: var(--accent);
}

.detail-symbol-box .atomic-number {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.detail-symbol-box .el-name {
    font-size: 1.2rem;
    font-weight: 600;
    margin-top: 0.5rem;
}

.detail-info {
    flex: 1;
}

.detail-info h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.detail-info .type-badge {
    display: inline-block;
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

.props-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 0.75rem;
}

.prop-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--bg-card);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.prop-item .label {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.prop-item .value {
    font-weight: 600;
    font-size: 0.95rem;
    text-align: right;
}

.compare-grid {
    display: grid;
    grid-template-columns: 1fr 200px 1fr;
    gap: 0;
    margin-top: 1.5rem;
}

.compare-grid .prop-label {
    text-align: center;
    padding: 0.6rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    font-size: 0.8rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.compare-grid .prop-val {
    padding: 0.6rem 1rem;
    background: var(--bg-card);
    border: 1px solid var(--border);
    font-size: 0.85rem;
    display: flex;
    align-items: center;
}

.compare-grid .prop-val:nth-child(3n+1) {
    justify-content: flex-end;
    text-align: right;
}

.compare-grid .prop-val:nth-child(3n) {
    justify-content: flex-start;
}

.compare-form {
    display: flex;
    gap: 1rem;
    align-items: flex-end;
    flex-wrap: wrap;
    margin-bottom: 1.5rem;
}

.compare-form .form-group {
    flex: 1;
    min-width: 200px;
}

.form-group label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 0.3rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.6rem 1rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.95rem;
    outline: none;
}

.form-group input:focus,
.form-group select:focus {
    border-color: var(--accent);
}

.form-group textarea {
    width: 100%;
    padding: 0.6rem 1rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.95rem;
    outline: none;
    resize: vertical;
}

.build-form {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1rem;
}

.alert {
    padding: 0.75rem 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
    font-size: 0.9rem;
}

.alert-success {
    background: rgba(102, 187, 106, 0.15);
    border: 1px solid var(--success);
    color: var(--success);
}

.alert-error {
    background: rgba(239, 83, 80, 0.15);
    border: 1px solid var(--danger);
    color: var(--danger);
}

.alert-info {
    background: rgba(79, 195, 247, 0.15);
    border: 1px solid var(--accent);
    color: var(--accent);
}

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

.sort-table th, .sort-table td {
    padding: 0.6rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

.sort-table th {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.sort-table tr:hover td {
    background: var(--bg-hover);
}

.sort-table td a {
    color: var(--text-primary);
}

.empty-state {
    text-align: center;
    padding: 3rem;
    color: var(--text-secondary);
}

.empty-state .icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.fav-btn {
    background: none;
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.fav-btn:hover {
    border-color: var(--warning);
    color: var(--warning);
}

.fav-btn.active {
    border-color: var(--warning);
    color: var(--warning);
    background: rgba(255, 167, 38, 0.1);
}

.random-box {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.5rem;
    text-align: center;
    margin-bottom: 1.5rem;
}

.random-box .symbol {
    font-size: 3rem;
    font-weight: 700;
    color: var(--accent);
}

.random-box .el-name {
    font-size: 1.2rem;
    margin: 0.5rem 0;
}

.stats-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.stat-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 1rem;
    text-align: center;
}

.stat-card .stat-number {
    font-size: 2rem;
    font-weight: 700;
    color: var(--accent);
}

.stat-card .stat-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.filter-pills {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-bottom: 1rem;
}

.filter-pill {
    padding: 0.3rem 0.7rem;
    border-radius: 20px;
    font-size: 0.75rem;
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    cursor: pointer;
    transition: all 0.2s;
}

.filter-pill:hover, .filter-pill.active {
    background: var(--accent);
    color: var(--bg-primary);
    border-color: var(--accent);
}

@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        gap: 0.5rem;
    }

    .nav-links {
        justify-content: center;
    }

    .elements-grid {
        grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    }

    .detail-header {
        flex-direction: column;
        align-items: center;
    }

    .compare-grid {
        grid-template-columns: 1fr;
    }

    .compare-grid .prop-label {
        background: var(--bg-hover);
        font-weight: 600;
    }
}