:root {
    --bg: #f5f7fb;
    --panel: #ffffff;
    --text: #1f2937;
    --muted: #6b7280;
    --primary: #0f766e;
    --primary-dark: #115e59;
    --success: #15803d;
    --error: #b91c1c;
    --border: #dbe2ea;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(180deg, #eef4ff 0%, var(--bg) 100%);
    color: var(--text);
}

a,
a:hover,
a:focus,
a:visited {
    text-decoration: none !important;
}

.container {
    width: min(1024px, 92vw);
    margin: 24px auto;
}

.card {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 18px;
    box-shadow: 0 8px 24px rgba(15, 23, 42, 0.06);
}

.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
}

.brand {
    font-size: 1.1rem;
    font-weight: 700;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 10px;
}

.nav-links a,
.btn {
    display: inline-block;
    text-decoration: none;
    border: none;
    border-radius: 10px;
    padding: 10px 14px;
    font-size: 0.95rem;
    cursor: pointer;
}

.btn,
.nav-links a.primary {
    background: var(--primary);
    color: #fff;
}

.btn:hover,
.nav-links a.primary:hover {
    background: var(--primary-dark);
}

.nav-links a.ghost {
    border: 1px solid var(--border);
    color: var(--text);
    background: #fff;
}

.btn.ghost-btn {
    border: 1px solid var(--border);
    color: var(--text);
    background: #fff;
}

.btn.ghost-btn:hover {
    background: #f3f4f6;
}

.grid {
    display: grid;
    gap: 14px;
}

.grid.stats {
    grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
}

.stat {
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 14px;
    background: #f8fafc;
}

.stat .label {
    color: var(--muted);
    font-size: 0.85rem;
}

.stat .value {
    margin-top: 4px;
    font-size: 1.3rem;
    font-weight: 700;
}

h1, h2, h3 {
    margin: 0 0 10px;
}

p {
    margin: 0 0 10px;
    color: var(--muted);
}

.form-group {
    margin-bottom: 12px;
}

label {
    display: block;
    margin-bottom: 6px;
    font-size: 0.9rem;
}

input[type="text"],
input[type="email"],
input[type="password"],
textarea {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 0.95rem;
}

.message {
    border-radius: 10px;
    padding: 10px 12px;
    margin-bottom: 12px;
}

.message.success {
    background: #ecfdf3;
    color: var(--success);
    border: 1px solid #b7ebc9;
}

.message.error {
    background: #fff1f2;
    color: var(--error);
    border: 1px solid #fecdd3;
}

.message.info {
    background: #eff6ff;
    color: #1e3a8a;
    border: 1px solid #bfdbfe;
}

.lesson-item {
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 12px;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    background: #fff;
}

.badge {
    display: inline-block;
    font-size: 0.78rem;
    border-radius: 999px;
    padding: 4px 10px;
    border: 1px solid var(--border);
    color: var(--muted);
}

.badge.done {
    background: #ecfdf3;
    color: var(--success);
    border-color: #b7ebc9;
}

.badge.locked {
    background: #f8fafc;
}

.question-options {
    display: grid;
    gap: 8px;
    margin: 12px 0;
}

.option {
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 8px 10px;
}

.voice-tools {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 10px 0 12px;
}

.question-audio {
    margin: 8px 0 14px;
}

.question-audio audio {
    width: min(420px, 100%);
}

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

.leaderboard-table th,
.leaderboard-table td {
    text-align: left;
    border-bottom: 1px solid var(--border);
    padding: 10px;
    font-size: 0.95rem;
}

.pwa-install-bar {
    position: fixed;
    left: 12px;
    right: 12px;
    bottom: 14px;
    z-index: 9999;
    display: none;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    padding: 10px 12px;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: rgba(255, 255, 255, 0.97);
    box-shadow: 0 8px 20px rgba(15, 23, 42, 0.14);
}

.pwa-install-bar.show {
    display: flex;
}

.pwa-install-text {
    font-size: 0.9rem;
    color: var(--text);
    font-weight: 600;
}

@media (max-width: 640px) {
    .lesson-item {
        flex-direction: column;
        align-items: flex-start;
    }

    .pwa-install-bar {
        flex-direction: column;
        align-items: stretch;
    }
}