* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: 'Segoe UI', 'Microsoft YaHei', sans-serif; background: #f0f4f8; color: #2d3748; line-height: 1.6; }
.container { max-width: 960px; margin: 0 auto; padding: 0 20px; }

.header { background: linear-gradient(135deg, #1a365d, #2b6cb0); color: #fff; padding: 16px 0; box-shadow: 0 2px 8px rgba(0,0,0,.15); position: sticky; top: 0; z-index: 100; }
.header .container { display: flex; align-items: center; justify-content: space-between; }
.logo { font-size: 1.3em; font-weight: 700; }
.nav-link { color: rgba(255,255,255,.8); text-decoration: none; margin-left: 20px; font-size: .9em; transition: color .2s; }
.nav-link:hover, .nav-link.active { color: #fff; }

/* Mode Selector */
.mode-selector { display: flex; gap: 10px; margin: 20px 0; }
.mode-btn { flex: 1; padding: 14px; border: 2px solid #cbd5e0; border-radius: 10px; background: #fff; cursor: pointer; font-size: 1.1em; font-weight: 600; transition: all .2s; }
.mode-btn.active { border-color: #2b6cb0; background: #ebf4ff; color: #2b6cb0; }
.mode-btn:hover { border-color: #2b6cb0; }

/* Filter Bar */
.filter-bar { display: flex; gap: 10px; margin-bottom: 16px; flex-wrap: wrap; }
.filter-bar select, .filter-bar input { padding: 8px 12px; border: 1px solid #cbd5e0; border-radius: 6px; font-size: .9em; }
.filter-bar select { min-width: 140px; }
.filter-bar input { flex: 1; min-width: 200px; }

/* Cards */
.card { background: #fff; border-radius: 10px; padding: 20px; margin-bottom: 12px; box-shadow: 0 1px 4px rgba(0,0,0,.08); transition: box-shadow .2s; }
.card:hover { box-shadow: 0 2px 12px rgba(0,0,0,.12); }
.card-header { display: flex; justify-content: space-between; align-items: flex-start; margin-bottom: 10px; }
.card-type { font-size: .8em; padding: 3px 10px; border-radius: 12px; color: #fff; font-weight: 600; }
.type-choice { background: #48bb78; }
.type-fill { background: #4299e1; }
.type-equation { background: #ed8936; }
.type-judgment { background: #9f7aea; }
.type-short_answer { background: #e53e3e; }

.card-question { font-size: 1em; margin-bottom: 12px; line-height: 1.7; white-space: pre-wrap; }
.card-options { margin-left: 16px; margin-bottom: 12px; }
.card-options label { display: block; padding: 6px 10px; cursor: pointer; border-radius: 6px; margin: 2px 0; transition: background .15s; }
.card-options label:hover { background: #f7fafc; }
.card-options input[type="radio"] { margin-right: 8px; }

.card-answer { margin-top: 8px; }
.card-answer textarea, .card-answer input { width: 100%; padding: 10px; border: 1px solid #cbd5e0; border-radius: 6px; font-size: .95em; }
.card-answer textarea { resize: vertical; min-height: 60px; }

.card-actions { display: flex; gap: 8px; margin-top: 12px; align-items: center; }
.card-result { margin-top: 8px; padding: 10px; border-radius: 6px; font-size: .9em; }
.result-correct { background: #c6f6d5; color: #22543d; }
.result-wrong { background: #fed7d7; color: #742a2a; }
.result-subjective { background: #fefcbf; color: #744210; }

/* Buttons */
.btn { padding: 8px 18px; border: 1px solid #cbd5e0; border-radius: 6px; background: #fff; cursor: pointer; font-size: .9em; font-weight: 500; transition: all .15s; }
.btn:hover { opacity: .85; }
.btn-primary { background: #2b6cb0; color: #fff; border-color: #2b6cb0; }
.btn-success { background: #38a169; color: #fff; border-color: #38a169; }
.btn-danger { background: #e53e3e; color: #fff; border-color: #e53e3e; }
.btn-warning { background: #ed8936; color: #fff; border-color: #ed8936; }
.btn-large { padding: 12px 32px; font-size: 1.1em; }
.btn-small { padding: 4px 10px; font-size: .8em; }

/* Exam */
.exam-start { text-align: center; padding: 40px 20px; background: #fff; border-radius: 10px; }
.exam-start h2 { font-size: 1.6em; margin-bottom: 10px; }
.exam-info { list-style: none; text-align: left; max-width: 400px; margin: 20px auto; }
.exam-info li { padding: 6px 0; }
.exam-header { display: flex; justify-content: space-between; padding: 10px 0; font-weight: 600; background: #fff; border-radius: 8px; padding: 12px 20px; margin-bottom: 16px; }
.exam-section { margin-bottom: 24px; }
.exam-section h3 { font-size: 1.15em; padding: 10px 16px; background: #2b6cb0; color: #fff; border-radius: 8px 8px 0 0; margin: 0; }

/* Admin */
.admin-login { max-width: 360px; margin: 60px auto; text-align: center; background: #fff; padding: 30px; border-radius: 10px; box-shadow: 0 2px 8px rgba(0,0,0,.1); }
.admin-login h2 { margin-bottom: 16px; }
.admin-login input { width: 100%; padding: 10px; border: 1px solid #cbd5e0; border-radius: 6px; margin-bottom: 12px; font-size: 1em; }
.admin-toolbar { display: flex; gap: 8px; margin-bottom: 16px; flex-wrap: wrap; align-items: center; }
.admin-toolbar select, .admin-toolbar input { padding: 8px 12px; border: 1px solid #cbd5e0; border-radius: 6px; font-size: .9em; }
.admin-toolbar input { flex: 1; min-width: 180px; }

/* Modal */
.modal { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,.5); display: flex; align-items: center; justify-content: center; z-index: 200; }
.modal-content { background: #fff; padding: 24px; border-radius: 10px; max-width: 500px; width: 90%; max-height: 85vh; overflow-y: auto; position: relative; }
.modal-large { max-width: 640px; }
.modal-close { position: absolute; right: 16px; top: 12px; font-size: 1.4em; cursor: pointer; color: #a0aec0; }
.modal-content h3 { margin-bottom: 12px; }
.modal-content label { display: block; margin: 8px 0 4px; font-weight: 600; font-size: .9em; }
.modal-content textarea, .modal-content input[type="text"], .modal-content input[type="number"], .modal-content select { width: 100%; padding: 8px 10px; border: 1px solid #cbd5e0; border-radius: 6px; font-size: .9em; }
.modal-content textarea { resize: vertical; }

/* Toast */
.toast { position: fixed; bottom: 30px; right: 30px; padding: 12px 24px; border-radius: 8px; color: #fff; font-weight: 500; z-index: 300; opacity: 0; transition: opacity .3s; pointer-events: none; }
.toast.show { opacity: 1; }
.toast-success { background: #38a169; }
.toast-error { background: #e53e3e; }
.toast-info { background: #2b6cb0; }

/* Pagination */
.pagination { display: flex; gap: 6px; justify-content: center; margin-top: 20px; }
.pagination button { padding: 6px 12px; border: 1px solid #cbd5e0; border-radius: 4px; background: #fff; cursor: pointer; }
.pagination button.active { background: #2b6cb0; color: #fff; border-color: #2b6cb0; }

/* Feedback */
.feedback-card { background: #fff; border-radius: 8px; padding: 16px; margin-bottom: 10px; box-shadow: 0 1px 3px rgba(0,0,0,.08); }
.feedback-card .meta { display: flex; gap: 16px; font-size: .85em; color: #718096; margin-top: 6px; }
.status-pending { color: #e53e3e; font-weight: 600; }
.status-resolved { color: #38a169; font-weight: 600; }
.status-rejected { color: #a0aec0; font-weight: 600; }

/* PDF progress */
.pdf-progress { padding: 12px; background: #ebf8ff; border-radius: 8px; margin-bottom: 12px; border: 1px solid #bee3f8; }

/* Responsive */
@media (max-width: 640px) {
    .container { padding: 0 12px; }
    .mode-btn { font-size: .95em; padding: 10px; }
    .admin-toolbar { flex-direction: column; align-items: stretch; }
}

/* Report button */
.report-btn { color: #a0aec0; cursor: pointer; font-size: .85em; background: none; border: none; margin-left: 8px; }
.report-btn:hover { color: #e53e3e; text-decoration: underline; }

/* Score display */
.score-badge { display: inline-flex; align-items: center; gap: 4px; padding: 4px 10px; border-radius: 20px; font-weight: 600; font-size: .85em; }
.score-correct { background: #c6f6d5; color: #22543d; }
.score-wrong { background: #fed7d7; color: #742a2a; }
.score-pending { background: #bee3f8; color: #2a4365; }

/* Markdown */
.markdown-body h1, .markdown-body h2, .markdown-body h3 { margin: 14px 0 8px; font-size: 1.15em; color: #1a365d; }
.markdown-body h1 { font-size: 1.3em; border-bottom: 1px solid #e2e8f0; padding-bottom: 6px; }
.markdown-body h2 { font-size: 1.2em; }
.markdown-body p { margin: 6px 0; }
.markdown-body ul, .markdown-body ol { margin: 6px 0; padding-left: 24px; }
.markdown-body li { margin: 3px 0; }
.markdown-body code { background: #edf2f7; padding: 2px 6px; border-radius: 3px; font-size: .9em; font-family: Consolas, monospace; }
.markdown-body pre { background: #2d3748; color: #e2e8f0; padding: 12px; border-radius: 6px; overflow-x: auto; margin: 10px 0; }
.markdown-body pre code { background: none; padding: 0; color: inherit; }
.markdown-body strong { font-weight: 700; color: #2b6cb0; }
.markdown-body blockquote { border-left: 3px solid #2b6cb0; margin: 8px 0; padding: 6px 14px; background: #ebf8ff; border-radius: 0 4px 4px 0; }
.markdown-body hr { border: none; border-top: 1px solid #e2e8f0; margin: 12px 0; }

/* Loading spinner */
.spinner { display: inline-block; width: 18px; height: 18px; border: 2px solid #cbd5e0; border-top-color: #2b6cb0; border-radius: 50%; animation: spin .6s linear infinite; margin-right: 6px; }
@keyframes spin { to { transform: rotate(360deg); } }