:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-main: #1f2937;
    --text-muted: #6b7280;
    --border-color: #e5e7eb;
    --badge-bg: #10b981;
    --error-color: #ef4444;
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
}

.hidden {
    display: none !important;
}

/* Modal */
.modal {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    backdrop-filter: blur(4px);
}

.modal-content {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    width: 90%;
    max-width: 400px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
    animation: slideUp 0.3s ease-out;
}

.modal-content h2 {
    margin-bottom: 1.5rem;
    text-align: center;
}

/* Forms */
input[type="text"], input[type="password"] {
    width: 100%;
    padding: 0.75rem;
    margin-bottom: 1rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
}

.btn-primary, .btn-secondary {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.2s;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    width: 100%;
}

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

.btn-secondary {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-main);
}

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

.error-text {
    color: var(--error-color);
    margin-top: 0.5rem;
    font-size: 0.875rem;
    text-align: center;
}

/* Layout */
header {
    background: var(--card-bg);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

main {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.upload-section {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}

#upload-form {
    display: flex;
    gap: 1rem;
    align-items: center;
    margin-top: 1rem;
}

@media (max-width: 768px) {
    #upload-form { flex-direction: column; }
    #upload-form > * { width: 100%; }
}

/* Gallery */
.gallery-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
}

.student-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    transition: transform 0.2s;
}

.student-card:hover {
    transform: translateY(-4px);
}

.student-name {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 1rem;
    border-bottom: 2px solid var(--bg-color);
    padding-bottom: 0.5rem;
}

.project-item {
    padding: 0.75rem;
    background: var(--bg-color);
    margin-bottom: 0.5rem;
    border-radius: 6px;
    cursor: pointer;
    transition: background 0.2s;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.project-item:hover {
    background: #e5e7eb;
}

.badge {
    background: var(--badge-bg);
    color: white;
    font-size: 0.75rem;
    padding: 0.2rem 0.5rem;
    border-radius: 99px;
    font-weight: 600;
}

/* Viewer */
.viewer-content {
    background: var(--card-bg);
    width: 95%;
    height: 90vh;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    animation: scaleUp 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.viewer-header {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.iframe-container {
    flex: 1;
    background: #fff;
}

iframe {
    width: 100%;
    height: 100%;
    border: none;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes scaleUp {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}