:root {
    color-scheme: light;
    --bg: #f5f7fb;
    --text: #162033;
    --muted: #5d6b82;
    --primary: #1b6ef3;
    --primary-dark: #1557c0;
    --surface: #ffffff;
    --border: #d9e1ee;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    font-family: Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
}

.page {
    min-height: 100vh;
    display: grid;
    place-items: center;
    padding: 24px;
}

.welcome,
.panel {
    width: min(100%, 720px);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 32px;
    box-shadow: 0 12px 30px rgba(22, 32, 51, 0.08);
}

.eyebrow {
    margin: 0 0 8px;
    color: var(--primary);
    font-size: 13px;
    font-weight: 700;
    text-transform: uppercase;
}

h1 {
    margin: 0 0 16px;
    font-size: 36px;
}

p {
    color: var(--muted);
    line-height: 1.6;
}

.actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 24px;
}

.form {
    display: grid;
    gap: 10px;
    margin-top: 22px;
}

.inline-form {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: center;
}

.inline-form select {
    min-height: 38px;
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 8px 10px;
    background: #ffffff;
    font: inherit;
}

.inline-form .button {
    min-height: 38px;
    padding: 0 12px;
}

.form label {
    font-weight: 700;
}

.form input,
.form select {
    width: 100%;
    min-height: 44px;
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 10px 12px;
    font: inherit;
    color: var(--text);
    background: #ffffff;
}

.form select {
    cursor: pointer;
}

.form textarea {
    width: 100%;
    min-height: 280px;
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 14px;
    font: 15px/1.55 Consolas, "Courier New", monospace;
    color: var(--text);
    background: #ffffff;
    resize: vertical;
}

.form input:focus,
.form select:focus {
    border-color: var(--primary);
    outline: 3px solid #dce9ff;
}

.form textarea:focus {
    border-color: var(--primary);
    outline: 3px solid #dce9ff;
}

.alert {
    margin-top: 18px;
    border: 1px solid #e4a4a4;
    border-radius: 6px;
    padding: 10px 14px;
    background: #fff2f2;
}

.alert p {
    margin: 4px 0;
    color: #8a2525;
}

.button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 42px;
    padding: 0 18px;
    border: 0;
    border-radius: 6px;
    background: var(--primary);
    color: #ffffff;
    font: inherit;
    font-weight: 700;
    text-decoration: none;
    cursor: pointer;
}

.button:hover {
    background: var(--primary-dark);
}

.button-secondary {
    background: #eef4ff;
    color: var(--primary-dark);
}

.button-secondary:hover {
    background: #dce9ff;
}

.status {
    margin-top: 24px;
    font-size: 14px;
}

.app-page {
    min-height: 100vh;
}

.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    min-height: 64px;
    padding: 0 32px;
    border-bottom: 1px solid var(--border);
    background: var(--surface);
}

.brand {
    color: var(--text);
    font-weight: 800;
    text-decoration: none;
}

.topbar-links {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 16px;
}

.topbar-links a,
.back-link {
    color: var(--primary-dark);
    font-weight: 700;
    text-decoration: none;
}

.content {
    width: min(1120px, 100%);
    margin: 0 auto;
    padding: 32px;
}

.section-heading {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 24px;
}

.section-heading h1,
.course-card h2,
.lesson-row h2,
.task-workspace h2,
.progress-row h2 {
    margin-top: 0;
}

.stats-grid,
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 16px;
    margin: 24px 0 32px;
}

.stat,
.course-card,
.lesson-row,
.task-workspace,
.progress-row {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
}

.stat {
    padding: 22px;
}

.stat span {
    display: block;
    color: var(--primary);
    font-size: 34px;
    font-weight: 800;
}

.stat p,
.meta {
    margin: 6px 0 0;
    color: var(--muted);
    font-size: 14px;
}

.course-card {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    padding: 22px;
}

.course-card h2,
.course-card h3 {
    margin: 0;
}

.empty,
.notice,
.hint {
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px;
    background: var(--surface);
}

.notice {
    margin-top: 18px;
    border-color: #9ad0aa;
    color: #1f6b35;
    background: #effaf1;
}

.hint {
    margin-top: 18px;
    background: #f8fbff;
}

.hint h3 {
    margin: 0 0 8px;
}

.lesson-list,
.progress-list {
    display: grid;
    gap: 14px;
}

.lesson-row,
.progress-row {
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: center;
    gap: 18px;
    padding: 20px;
}

.task-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 20px;
    align-items: start;
}

.task-list {
    display: grid;
    gap: 8px;
}

.task-list a {
    display: grid;
    gap: 4px;
    padding: 14px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--surface);
    color: var(--text);
    text-decoration: none;
}

.task-list a.active {
    border-color: var(--primary);
    outline: 3px solid #dce9ff;
}

.task-list span {
    color: var(--muted);
    font-size: 13px;
}

.task-workspace {
    padding: 24px;
}

.editor-shell {
    display: grid;
    gap: 14px;
}

.editor-toolbar {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: space-between;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 10px 12px;
    background: #f8fbff;
    color: var(--muted);
    font-size: 14px;
    font-weight: 700;
}

.live-preview {
    width: 100%;
    min-height: 260px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: #ffffff;
}

.progress-row {
    grid-template-columns: 1fr minmax(180px, 280px) 56px;
}

.progress-meter {
    height: 10px;
    overflow: hidden;
    border-radius: 999px;
    background: #dbe4f0;
}

.progress-meter span {
    display: block;
    height: 100%;
    border-radius: inherit;
    background: var(--primary);
}

.split-layout,
.review-layout {
    display: grid;
    gap: 20px;
    align-items: start;
}

.split-layout {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin-bottom: 32px;
}

.review-layout {
    grid-template-columns: minmax(0, 1.2fr) minmax(320px, 0.8fr);
}

.table-wrap {
    overflow-x: auto;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--surface);
}

table {
    width: 100%;
    border-collapse: collapse;
    min-width: 680px;
}

th,
td {
    padding: 12px 14px;
    border-bottom: 1px solid var(--border);
    text-align: left;
    vertical-align: top;
}

th {
    color: var(--muted);
    font-size: 13px;
    text-transform: uppercase;
}

td a {
    color: var(--primary-dark);
    font-weight: 700;
    text-decoration: none;
}

tr:last-child td {
    border-bottom: 0;
}

.code-preview {
    max-height: 360px;
    overflow: auto;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px;
    background: #0f1724;
    color: #e8eef8;
    font: 14px/1.55 Consolas, "Courier New", monospace;
    white-space: pre-wrap;
}

.expected-source {
    max-height: 280px;
    overflow: auto;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 14px;
    background: #f5f7fb;
    color: var(--text);
    font: 14px/1.55 Consolas, "Courier New", monospace;
    white-space: pre-wrap;
}

@media (max-width: 760px) {
    .topbar,
    .section-heading,
    .lesson-row,
    .progress-row {
        display: grid;
    }

    .topbar {
        padding: 16px;
    }

    .content {
        padding: 20px 16px;
    }

    .task-layout {
        grid-template-columns: 1fr;
    }

    .split-layout,
    .review-layout {
        grid-template-columns: 1fr;
    }

    .progress-row {
        grid-template-columns: 1fr;
    }
}