:root {
    --bg-color: #ffffff;
    --text-color: #1e293b;
    --text-muted: #64748b;
    --card-bg: #f8fafc;
    --card-border: #e2e8f0;
    --primary: #ef4444;
    --primary-hover: #dc2626;
    --header-bg: rgba(255, 255, 255, 0.8);
}
html.dark {
    --bg-color: #080b11;
    --text-color: #f1f5f9;
    --text-muted: #94a3b8;
    --card-bg: rgba(17, 24, 39, 0.7);
    --card-border: #1f2937;
    --primary: #ef4444;
    --primary-hover: #f87171;
    --header-bg: rgba(8, 11, 17, 0.8);
}
html:not(.editing-mode) .admin-only {
    display: none !important;
}
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Outfit', sans-serif;
}
body {
    background: var(--bg-color);
    color: var(--text-color);
    min-height: 100vh;
    position: relative;
    overflow-x: hidden;
    transition: background-color 0.3s, color 0.3s;
    display: flex;
    flex-direction: column;
}
#math-bg {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    pointer-events: none;
}
.top-nav {
    position: sticky;
    top: 0;
    z-index: 50;
    background: var(--header-bg);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--card-border);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.logo-area {
    display: flex;
    align-items: center;
    gap: 1rem;
    text-decoration: none;
}
.logo-img {
    height: 40px;
    width: 40px;
    border-radius: 8px;
}
.logo-text {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    letter-spacing: -0.5px;
}
.theme-switch {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 32px;
    z-index: 100;
}
.theme-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}
.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--card-bg);
    border: 1px solid var(--card-border);
    transition: .4s;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 6px;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.1);
    backdrop-filter: blur(8px);
}
.slider.round {
    border-radius: 34px;
}
.slider:before {
    position: absolute;
    content: "";
    height: 24px;
    width: 24px;
    left: 3px;
    bottom: 3px;
    background-color: var(--text-color);
    transition: .4s;
    border-radius: 50%;
    z-index: 2;
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}
input:checked + .slider {
    background-color: var(--primary);
    border-color: var(--primary);
}
input:checked + .slider:before {
    transform: translateX(28px);
    background-color: #fff;
}
.icon {
    font-size: 13px;
    z-index: 1;
    user-select: none;
}
.sun { color: #f59e0b; }
.moon { color: #f1f5f9; }

.btn {
    display: inline-block;
    text-align: center;
    background: var(--primary);
    color: #ffffff;
    text-decoration: none;
    padding: 0.6rem 1.2rem;
    border-radius: 0.75rem;
    font-weight: 600;
    transition: opacity 0.2s;
    border: none;
    cursor: pointer;
}
.btn:hover {
    opacity: 0.9;
}
.glass-panel {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(8px);
    border-radius: 1.25rem;
}
/* Form components */
.form-group { display: flex; flex-direction: column; gap: 0.5rem; margin-bottom: 1rem; width: 100%; }
.form-group label { font-size: 0.95rem; font-weight: 600; color: var(--text-muted); }
.form-group input, .form-group select, .form-group textarea { padding: 0.8rem 1rem; border-radius: 0.75rem; border: 1px solid var(--card-border); background: rgba(255,255,255,0.05); color: var(--text-color); outline: none; width: 100%; box-sizing: border-box; }
.form-group input[type="file"] { padding: 0.5rem; }

/* Dropdown */
.dropdown-container { position: relative; display: inline-block; }
.dropdown-menu {
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: 0.5rem;
    background: var(--header-bg);
    border: 1px solid var(--card-border);
    border-radius: 0.75rem;
    padding: 0.5rem;
    min-width: 150px;
    box-shadow: 0 10px 25px -5px rgba(0,0,0,0.3);
    backdrop-filter: blur(12px);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all 0.2s ease;
    z-index: 100;
}
.dropdown-container:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.dropdown-item {
    display: block;
    padding: 0.6rem 1rem;
    color: var(--text-color);
    text-decoration: none;
    border-radius: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    transition: background 0.2s;
}
.dropdown-item:hover {
    background: rgba(255,255,255,0.1);
    color: var(--primary);
}
.dropdown-item.text-danger:hover {
    background: rgba(239, 68, 68, 0.1);
    color: #ef4444;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    flex: 1;
    width: 100%;
}
.hero {
    text-align: center;
    margin: 3rem 0 5rem 0;
}
.hero h1 {
    font-size: 3.5rem;
    color: var(--text-color);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1rem;
}
.hero h1 span {
    color: var(--primary);
}
.hero p {
    color: var(--text-muted);
    font-size: 1.25rem;
    max-width: 600px;
    margin: 0 auto;
}
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}
.card {
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: transform 0.3s, box-shadow 0.3s;
}
.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px -5px rgba(239, 68, 68, 0.2);
    border-color: var(--primary);
}
.card-thumb {
    height: 160px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(239, 68, 68, 0.1);
    font-size: 5rem;
    border-bottom: 1px solid var(--card-border);
}
.card-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}
.card-body {
    padding: 1.5rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}
.card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}
.card p {
    color: var(--text-muted);
    font-size: 0.95rem;
    line-height: 1.5;
    margin-bottom: 1.5rem;
    flex: 1;
}
.category-section {
    margin-bottom: 4rem;
}
.category-title {
    font-size: 2rem;
    color: var(--text-color);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}
select option {
    background-color: var(--bg-color);
    color: var(--text-color);
}
.course-layout {
    grid-template-columns: 350px 1fr;
}
@media (max-width: 768px) {
    .top-nav {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }
}

html.editing-mode [draggable="true"] {
    cursor: grab;
}
html.editing-mode [draggable="true"]:active {
    cursor: grabbing;
}

@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }
    .courses-grid {
        grid-template-columns: 1fr !important;
    }
    .category-section {
        flex-direction: column !important;
        text-align: center;
        gap: 1rem !important;
        padding: 1.5rem !important;
    }
    .course-layout {
        display: flex !important;
        flex-direction: column-reverse;
        gap: 2rem;
    }
    .sidebar {
        position: static !important;
        width: 100%;
    }
    .container {
        padding: 1rem;
    }
    .category-title {
        font-size: 1.5rem;
        flex-direction: column;
        text-align: center;
    }
}