:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --success: #16a34a;
    --danger: #dc2626;
    --warning: #d97706;
    --bg: #f4f6f9;
    --card-bg: #ffffff;
    --border: #e2e8f0;
    --text: #1e293b;
    --text-light: #64748b;
    --radius: 10px;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: -apple-system, "Segoe UI", "Microsoft JhengHei", "PingFang TC", sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 1100px; margin: 0 auto; padding: 24px 16px 60px; }
.container-narrow { max-width: 480px; margin: 60px auto; padding: 0 16px; }

/* Navbar */
.navbar {
    background: #fff;
    border-bottom: 1px solid var(--border);
    padding: 12px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
}
.navbar .brand { font-weight: 700; font-size: 18px; color: var(--primary-dark); }
.navbar .nav-right { display: flex; align-items: center; gap: 14px; font-size: 14px; }
.navbar .nav-right span { color: var(--text-light); }
.navbar-admin { background: #0f172a; border-bottom: 1px solid #1e293b; }
.navbar-admin .brand { color: #fff; }

.tabs {
    display: flex;
    gap: 4px;
    border-bottom: 1px solid var(--border);
    margin-bottom: 20px;
    flex-wrap: wrap;
}
.tabs a {
    padding: 10px 16px;
    color: var(--text-light);
    border-bottom: 2px solid transparent;
    font-size: 14px;
    font-weight: 500;
}
.tabs a.active, .tabs a:hover {
    color: var(--primary-dark);
    border-bottom-color: var(--primary);
    text-decoration: none;
}

/* Card */
.card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 22px;
    margin-bottom: 20px;
}
.card h2, .card h3 { margin-top: 0; }

.grid { display: grid; gap: 16px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 720px) {
    .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
}

/* Form */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; margin-bottom: 6px; font-size: 14px; font-weight: 600; color: var(--text); }
input[type=text], input[type=email], input[type=password], input[type=number],
input[type=date], input[type=datetime-local], select, textarea {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 14px;
    background: #fff;
    color: var(--text);
    font-family: inherit;
}
input:focus, select:focus, textarea:focus { outline: none; border-color: var(--primary); }
.form-row { display: flex; gap: 12px; }
.form-row > div { flex: 1; }

/* Buttons */
.btn {
    display: inline-block;
    padding: 10px 18px;
    border-radius: 8px;
    border: none;
    background: var(--primary);
    color: #fff;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    text-align: center;
}
.btn:hover { background: var(--primary-dark); text-decoration: none; color: #fff; }
.btn-sm { padding: 6px 12px; font-size: 13px; }
.btn-outline { background: #fff; color: var(--primary); border: 1px solid var(--primary); }
.btn-outline:hover { background: #eff6ff; color: var(--primary-dark); }
.btn-danger { background: var(--danger); }
.btn-danger:hover { background: #b91c1c; }
.btn-success { background: var(--success); }
.btn-success:hover { background: #15803d; }
.btn-block { width: 100%; }

/* Table */
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { padding: 10px 12px; border-bottom: 1px solid var(--border); text-align: left; }
th { background: #f8fafc; font-weight: 700; color: var(--text-light); font-size: 13px; }
tr:hover td { background: #f8fafc; }
.table-wrap { overflow-x: auto; }

/* Badges */
.badge { display: inline-block; padding: 3px 10px; border-radius: 999px; font-size: 12px; font-weight: 600; }
.badge-success { background: #dcfce7; color: #166534; }
.badge-danger { background: #fee2e2; color: #991b1b; }
.badge-warning { background: #fef3c7; color: #92400e; }
.badge-gray { background: #f1f5f9; color: #475569; }

/* Alerts */
.alert { padding: 12px 16px; border-radius: 8px; margin-bottom: 16px; font-size: 14px; }
.alert-success { background: #dcfce7; color: #166534; border: 1px solid #86efac; }
.alert-danger { background: #fee2e2; color: #991b1b; border: 1px solid #fca5a5; }
.alert-info { background: #dbeafe; color: #1e40af; border: 1px solid #93c5fd; }

/* Stat boxes */
.stat-box { background: #fff; border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; text-align: center; }
.stat-box .label { font-size: 13px; color: var(--text-light); margin-bottom: 6px; }
.stat-box .value { font-size: 24px; font-weight: 700; color: var(--primary-dark); }

.class-code-box {
    background: #eff6ff;
    border: 1px dashed var(--primary);
    border-radius: 8px;
    padding: 14px 16px;
    font-family: monospace;
    font-size: 14px;
    word-break: break-all;
}

.text-muted { color: var(--text-light); font-size: 13px; }
.text-center { text-align: center; }
.mt-0 { margin-top: 0; }
.mb-0 { margin-bottom: 0; }
.flex { display: flex; align-items: center; gap: 10px; }
.flex-between { display: flex; align-items: center; justify-content: space-between; }

.empty-state { text-align: center; padding: 40px 20px; color: var(--text-light); }

.score-input { width: 90px; }

/* 密碼顯示/隱藏切換（實際定位由 main.js 以行內樣式套用，此處為備用/微調樣式） */
.password-wrapper { position: relative; width: 100%; }
.toggle-password { border-radius: 6px; }
.toggle-password:hover { background: #f1f5f9; }

/* 重設密碼摺疊區塊 */
details.inline-reset { display: inline-block; }
details.inline-reset summary {
    cursor: pointer;
    list-style: none;
    color: var(--primary);
    font-size: 13px;
    font-weight: 600;
    padding: 4px 10px;
    border: 1px solid var(--primary);
    border-radius: 6px;
    display: inline-block;
}
details.inline-reset summary::-webkit-details-marker { display: none; }
details.inline-reset .reset-panel {
    margin-top: 8px;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: #f8fafc;
    min-width: 220px;
}

/* 簽到區塊 */
.checkin-box {
    background: linear-gradient(135deg, #eff6ff, #f0fdf4);
    border: 1px solid #bfdbfe;
    border-radius: var(--radius);
    padding: 20px;
    text-align: center;
    margin-bottom: 20px;
}
.checkin-box .time { font-size: 28px; font-weight: 700; color: var(--primary-dark); margin: 6px 0; }
.checkin-box .status-done { color: var(--success); font-weight: 700; font-size: 18px; }