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

:root {
    --primary: #0891b2;
    --primary-dark: #0e7490;
    --secondary: #1e293b;
    --accent: #d97706;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --bg-light: #f8fafc;
    --bg-dark: #0f172a;
    --card-bg: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-light);
    color: var(--text);
    min-height: 100vh;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--secondary) 0%, #334155 100%);
    color: white;
    padding: 20px 40px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}

.header h1 {
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    gap: 10px;
}

.header h1 span {
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-actions {
    display: flex;
    gap: 15px;
}

/* Buttons */
.btn {
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(8, 145, 178, 0.3);
}

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

.btn-secondary:hover {
    background: #334155;
}

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

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

.btn-outline {
    background: transparent;
    border: 2px solid var(--primary);
    color: var(--primary);
}

.btn-outline:hover {
    background: var(--primary);
    color: white;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.85rem;
}

/* Container */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 30px;
}

/* Cards */
.card {
    background: var(--card-bg);
    border-radius: 16px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05);
    padding: 25px;
    margin-bottom: 20px;
    border: 1px solid var(--border);
    transition: all 0.3s ease;
}

.card:hover {
    box-shadow: 0 8px 30px rgba(0,0,0,0.1);
    transform: translateY(-2px);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border);
}

.card-title {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--secondary);
}

/* Presentations Grid */
.presentations-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 25px;
    margin-top: 20px;
}

.presentation-card {
    background: var(--card-bg);
    border-radius: 16px;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05);
    border: 1px solid var(--border);
    transition: all 0.3s ease;
}

.presentation-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px rgba(0,0,0,0.12);
}

.presentation-thumbnail {
    width: 100%;
    height: 200px;
    background: linear-gradient(135deg, var(--secondary) 0%, #475569 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.presentation-thumbnail.dark {
    background: linear-gradient(135deg, #0a1628 0%, #1e3a5f 100%);
}

.presentation-thumbnail.light {
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
}

.presentation-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.presentation-thumbnail .overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.presentation-card:hover .overlay {
    opacity: 1;
}

.presentation-info {
    padding: 20px;
}

.presentation-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--secondary);
}

.presentation-meta {
    display: flex;
    justify-content: space-between;
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: 15px;
}

.presentation-actions {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

/* Forms */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--secondary);
}

.form-control {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid var(--border);
    border-radius: 10px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(8, 145, 178, 0.1);
}

/* Modal */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--card-bg);
    border-radius: 20px;
    padding: 30px;
    max-width: 500px;
    width: 90%;
    transform: scale(0.9);
    transition: transform 0.3s ease;
}

.modal-overlay.active .modal {
    transform: scale(1);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 25px;
}

.modal-title {
    font-size: 1.4rem;
    font-weight: 600;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
}

/* Share Options */
.share-options {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.share-option {
    flex: 1;
    padding: 15px;
    border: 2px solid var(--border);
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
}

.share-option:hover,
.share-option.active {
    border-color: var(--primary);
    background: rgba(8, 145, 178, 0.05);
}

.share-option i {
    font-size: 1.5rem;
    color: var(--primary);
    margin-bottom: 8px;
}

.share-option span {
    display: block;
    font-size: 0.9rem;
    color: var(--text-muted);
}

/* Share Link Box */
.share-link-box {
    background: var(--bg-light);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 15px;
    display: flex;
    gap: 10px;
    align-items: center;
}

.share-link-box input {
    flex: 1;
    background: none;
    border: none;
    font-size: 0.9rem;
    color: var(--text);
}

/* Stats */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 20px;
    text-align: center;
    border: 1px solid var(--border);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary);
}

.stat-label {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 5px;
}

/* Table */
.table-container {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 15px;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

th {
    background: var(--bg-light);
    font-weight: 600;
    color: var(--secondary);
}

tr:hover {
    background: rgba(8, 145, 178, 0.02);
}

/* Badge */
.badge {
    display: inline-block;
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 500;
}

.badge-success {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success);
}

.badge-warning {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning);
}

.badge-danger {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

/* Login Page */
.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--secondary) 0%, #475569 100%);
}

.login-box {
    background: var(--card-bg);
    border-radius: 20px;
    padding: 40px;
    width: 400px;
    max-width: 90%;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
}

.login-header {
    text-align: center;
    margin-bottom: 30px;
}

.login-header h1 {
    font-size: 1.8rem;
    color: var(--secondary);
    margin-bottom: 10px;
}

.login-header p {
    color: var(--text-muted);
}

/* Alert */
.alert {
    padding: 15px 20px;
    border-radius: 10px;
    margin-bottom: 20px;
}

.alert-danger {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
    border: 1px solid rgba(239, 68, 68, 0.2);
}

.alert-success {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success);
    border: 1px solid rgba(16, 185, 129, 0.2);
}

/* Presentation Viewer */
.viewer-container {
    width: 100vw;
    height: 100vh;
    display: flex;
    flex-direction: column;
}

.viewer-header {
    background: var(--secondary);
    color: white;
    padding: 10px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.viewer-frame {
    flex: 1;
    border: none;
    width: 100%;
}

/* Responsive */
@media (max-width: 768px) {
    .header {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }

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

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

    .container {
        padding: 15px;
    }

    .share-options {
        flex-direction: column;
    }
}