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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 800px;
    margin: 0 auto;
}

/* Header */
header {
    text-align: center;
    color: white;
    padding: 30px 0 25px;
    position: relative;
}

header h1 {
    font-size: 2.2rem;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0,0,0,0.2);
    margin-bottom: 8px;
}

header .subtitle {
    font-size: 1rem;
    opacity: 0.9;
    margin-bottom: 15px;
}

.btn-view-all {
    display: inline-block;
    background: rgba(255,255,255,0.2);
    color: white;
    text-decoration: none;
    padding: 8px 20px;
    border-radius: 20px;
    font-size: 0.9rem;
    border: 1px solid rgba(255,255,255,0.4);
    transition: background 0.2s;
}

.btn-view-all:hover {
    background: rgba(255,255,255,0.35);
}

/* Card */
.card {
    background: white;
    border-radius: 16px;
    padding: 32px;
    margin-bottom: 20px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.15);
}

/* Form */
.form-group {
    margin-bottom: 24px;
}

.form-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 8px;
    color: #444;
    font-size: 0.95rem;
}

.form-group input[type="text"] {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid #e0e0e0;
    border-radius: 10px;
    font-size: 1rem;
    transition: border-color 0.2s;
    outline: none;
    font-family: inherit;
}

.form-group input[type="text"]:focus {
    border-color: #667eea;
}

.form-group small {
    color: #888;
    font-size: 0.82rem;
    margin-top: 5px;
    display: block;
}

.form-group code {
    background: #f0f0f0;
    padding: 1px 6px;
    border-radius: 4px;
    font-size: 0.85rem;
}

/* Drop zone */
.drop-zone {
    border: 2px dashed #c0b4f0;
    border-radius: 12px;
    padding: 30px 20px;
    text-align: center;
    background: #f9f7ff;
    transition: all 0.2s;
    cursor: pointer;
}

.drop-zone.drag-over {
    border-color: #667eea;
    background: #f0eeff;
}

.drop-icon {
    font-size: 2.5rem;
    margin-bottom: 8px;
}

.drop-zone p {
    color: #666;
    margin-bottom: 10px;
}

.drop-zone .hint {
    font-size: 0.8rem;
    color: #999;
    margin-top: 8px;
}

.btn-choose {
    display: inline-block;
    background: #667eea;
    color: white;
    padding: 8px 22px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: background 0.2s;
}

.btn-choose:hover {
    background: #5a6fd6;
}

/* File list */
.file-list {
    margin-top: 12px;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.file-tag {
    background: #eef0ff;
    color: #667eea;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.82rem;
    border: 1px solid #d0d5ff;
}

/* Submit button */
.btn-submit {
    display: inline-block;
    width: 100%;
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    padding: 15px;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    text-align: center;
    text-decoration: none;
    transition: opacity 0.2s, transform 0.1s;
    font-family: inherit;
}

.btn-submit:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

.btn-submit:active {
    transform: translateY(0);
}

.btn-secondary {
    display: inline-block;
    background: #f0f0f0;
    color: #555;
    border: none;
    padding: 12px 24px;
    border-radius: 10px;
    font-size: 0.95rem;
    text-decoration: none;
    transition: background 0.2s;
}

.btn-secondary:hover {
    background: #e0e0e0;
}

/* Info box */
.info-box {
    background: rgba(255,255,255,0.15);
    border-radius: 12px;
    padding: 20px 24px;
    color: white;
    margin-bottom: 20px;
}

.info-box h3 {
    margin-bottom: 12px;
    font-size: 1rem;
}

.info-box ol {
    padding-left: 20px;
    line-height: 1.9;
    font-size: 0.92rem;
}

.info-box strong {
    font-weight: 600;
}

.info-box code {
    background: rgba(255,255,255,0.25);
    padding: 1px 6px;
    border-radius: 4px;
}

.info-box .note {
    margin-top: 12px;
    font-size: 0.85rem;
    opacity: 0.85;
}

/* Alerts */
.alert {
    padding: 14px 18px;
    border-radius: 10px;
    margin-bottom: 18px;
    font-size: 0.95rem;
}

.alert-error {
    background: #ffe5e5;
    color: #c0392b;
    border: 1px solid #ffb3b3;
}

.alert-warning {
    background: #fff8e1;
    color: #856404;
    border: 1px solid #ffe082;
    margin-top: 16px;
}

/* Success page */
.success-card {
    text-align: center;
}

.success-icon {
    font-size: 4rem;
    margin-bottom: 12px;
}

.success-card h2 {
    font-size: 1.6rem;
    color: #2d8a4e;
    margin-bottom: 8px;
}

.student-name {
    font-size: 1.2rem;
    font-weight: 600;
    color: #444;
    margin-bottom: 4px;
}

.upload-time {
    color: #888;
    font-size: 0.88rem;
    margin-bottom: 24px;
}

.link-box {
    background: #f5f5ff;
    border-radius: 10px;
    padding: 16px;
    margin-bottom: 20px;
    text-align: left;
}

.link-box label {
    font-weight: 600;
    color: #555;
    font-size: 0.9rem;
    display: block;
    margin-bottom: 8px;
}

.link-row {
    display: flex;
    gap: 8px;
}

.link-row input {
    flex: 1;
    padding: 10px 14px;
    border: 2px solid #d0d5ff;
    border-radius: 8px;
    font-size: 0.85rem;
    background: white;
    color: #555;
    outline: none;
    font-family: monospace;
}

.btn-copy {
    background: #667eea;
    color: white;
    border: none;
    padding: 10px 16px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.88rem;
    white-space: nowrap;
    font-family: inherit;
    transition: background 0.2s;
}

.btn-copy:hover {
    background: #5a6fd6;
}

.action-buttons {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 20px;
}

.action-buttons .btn-submit {
    width: auto;
    padding: 12px 28px;
    font-size: 0.95rem;
}

.file-summary {
    text-align: left;
    background: #f9f9f9;
    border-radius: 10px;
    padding: 14px 18px;
    margin-top: 12px;
}

.file-summary h4 {
    font-size: 0.9rem;
    color: #555;
    margin-bottom: 8px;
}

.file-summary ul {
    padding-left: 18px;
    font-size: 0.85rem;
    color: #666;
    line-height: 1.8;
}

/* Projects grid */
.total-count {
    color: white;
    text-align: center;
    margin-bottom: 16px;
    font-size: 0.95rem;
    opacity: 0.9;
}

.projects-grid {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 20px;
}

.project-card {
    background: white;
    border-radius: 14px;
    padding: 18px 20px;
    display: flex;
    align-items: center;
    gap: 16px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
    transition: transform 0.15s, box-shadow 0.15s;
}

.project-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.project-thumb {
    width: 56px;
    height: 56px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.project-initial {
    color: white;
    font-size: 1.5rem;
    font-weight: 700;
}

.project-info {
    flex: 1;
}

.project-info h3 {
    font-size: 1.05rem;
    color: #333;
    margin-bottom: 4px;
}

.project-time,
.project-files {
    font-size: 0.82rem;
    color: #888;
    margin-bottom: 2px;
}

.btn-view {
    display: inline-block;
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    text-decoration: none;
    padding: 9px 18px;
    border-radius: 8px;
    font-size: 0.88rem;
    white-space: nowrap;
    transition: opacity 0.2s;
}

.btn-view:hover {
    opacity: 0.85;
}

/* Empty state */
.empty-state {
    text-align: center;
    color: white;
    padding: 60px 20px;
}

.empty-state h3 {
    font-size: 1.3rem;
    margin: 16px 0 24px;
    opacity: 0.9;
}

.empty-state .btn-submit {
    width: auto;
    padding: 12px 30px;
    display: inline-block;
    font-size: 1rem;
}

/* Responsive */
@media (max-width: 600px) {
    header h1 {
        font-size: 1.6rem;
    }

    .card {
        padding: 20px;
    }

    .project-card {
        flex-wrap: wrap;
    }

    .action-buttons {
        flex-direction: column;
    }

    .link-row {
        flex-direction: column;
    }
}