:root {
    /* Light Mode */
    --bg-color: #f8fafc;
    --surface-color: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --danger-color: #ef4444;
    --success-color: #10b981;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius-md: 0.375rem;
    --radius-lg: 0.5rem;
    --radius-xl: 0.75rem;
}

@media (prefers-color-scheme: dark) {
    :root {
        /* Dark Mode */
        --bg-color: #0f172a;
        --surface-color: #1e293b;
        --text-primary: #f8fafc;
        --text-secondary: #94a3b8;
        --border-color: #334155;
        --primary-color: #6366f1;
        --primary-hover: #818cf8;
        --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
        --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
        --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
    }
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background-color 0.3s, color 0.3s;
}

a {
    color: var(--primary-color);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Typography */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }
.font-bold { font-weight: 700; }
.font-semibold { font-weight: 600; }
.text-sm { font-size: 0.875rem; }
.text-xs { font-size: 0.75rem; }
.text-lg { font-size: 1.125rem; }
.text-xl { font-size: 1.25rem; }
.text-2xl { font-size: 1.5rem; }
.text-3xl { font-size: 1.875rem; }
.text-primary { color: var(--primary-color); }
.text-secondary { color: var(--text-secondary); }
.text-danger { color: var(--danger-color); }
.text-success { color: var(--success-color); }

/* Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem;
}
.max-w-md { max-width: 28rem; }
.max-w-lg { max-width: 32rem; }
.max-w-xl { max-width: 36rem; }
.max-w-2xl { max-width: 42rem; }
.max-w-3xl { max-width: 48rem; }
.mx-auto { margin-left: auto; margin-right: auto; }
.w-full { width: 100%; }
.h-full { height: 100%; }

/* Flexbox */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: 0.25rem; }
.gap-2 { gap: 0.5rem; }
.gap-4 { gap: 1rem; }
.gap-6 { gap: 1.5rem; }

/* Grid */
.grid { display: grid; }
.grid-cols-1 { grid-template-columns: repeat(1, minmax(0, 1fr)); }
.grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
@media (min-width: 768px) {
    .md\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .md\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}

/* Spacing */
.p-2 { padding: 0.5rem; }
.p-4 { padding: 1rem; }
.p-6 { padding: 1.5rem; }
.p-8 { padding: 2rem; }
.px-4 { padding-left: 1rem; padding-right: 1rem; }
.py-2 { padding-top: 0.5rem; padding-bottom: 0.5rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-4 { margin-top: 1rem; }
.mt-6 { margin-top: 1.5rem; }
.mt-8 { margin-top: 2rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-4 { margin-bottom: 1rem; }
.mb-6 { margin-bottom: 1.5rem; }

/* UI Elements */
.card {
    background-color: var(--surface-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    overflow: hidden;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 1rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    font-size: 1rem;
}
.btn-primary {
    background-color: var(--primary-color);
    color: white;
}
.btn-primary:hover {
    background-color: var(--primary-hover);
}
.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}
.btn-outline {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}
.btn-outline:hover {
    background-color: var(--border-color);
}

.input, .select {
    width: 100%;
    padding: 0.5rem 0.75rem;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color 0.2s;
}
.input:focus, .select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 1px var(--primary-color);
}

.label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 0.25rem;
    color: var(--text-primary);
}

/* Checkbox Toggle / Switch */
.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
}
.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}
.slider {
    position: absolute;
    cursor: pointer;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: var(--border-color);
    transition: .4s;
    border-radius: 24px;
}
.slider:before {
    position: absolute;
    content: "";
    height: 18px;
    width: 18px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: .4s;
    border-radius: 50%;
}
input:checked + .slider {
    background-color: var(--primary-color);
}
input:checked + .slider:before {
    transform: translateX(20px);
}

/* Drag & Drop Zone */
.drop-zone {
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    text-align: center;
    background-color: var(--surface-color);
    transition: all 0.2s;
    cursor: pointer;
}
.drop-zone:hover, .drop-zone.drag-active {
    border-color: var(--primary-color);
    background-color: rgba(99, 102, 241, 0.05);
}
.drop-zone-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* Progress Bar */
.progress-bg {
    width: 100%;
    height: 0.75rem;
    background-color: var(--border-color);
    border-radius: 999px;
    overflow: hidden;
}
.progress-fill {
    height: 100%;
    background-color: var(--primary-color);
    border-radius: 999px;
    transition: width 0.3s ease;
}

/* Navigation */
.nav-header {
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    margin-bottom: 2rem;
}
.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}
.nav-links {
    display: flex;
    gap: 1.5rem;
}
.nav-links a {
    color: var(--text-secondary);
    font-weight: 500;
}
.nav-links a:hover, .nav-links a.active {
    color: var(--primary-color);
}

/* Status Badges */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.625rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 500;
}
.badge-success {
    background-color: rgba(16, 185, 129, 0.1);
    color: var(--success-color);
}
.badge-warning {
    background-color: rgba(245, 158, 11, 0.1);
    color: #f59e0b;
}
.badge-danger {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--danger-color);
}
.badge-primary {
    background-color: rgba(99, 102, 241, 0.1);
    color: var(--primary-color);
}

/* Table */
.table-container {
    overflow-x: auto;
}
table {
    width: 100%;
    border-collapse: collapse;
}
th {
    text-align: left;
    padding: 0.75rem 1rem;
    background-color: var(--bg-color);
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.875rem;
    border-bottom: 1px solid var(--border-color);
}
td {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-primary);
    font-size: 0.875rem;
}
tr:last-child td {
    border-bottom: none;
}
tr:hover td {
    background-color: rgba(0, 0, 0, 0.02);
}
@media (prefers-color-scheme: dark) {
    tr:hover td {
        background-color: rgba(255, 255, 255, 0.02);
    }
}