:root {
    --bg: #f5f7fb;
    --panel: #ffffff;
    --ink: #1c2634;
    --muted: #6b7685;
    --line: #dfe5ee;
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --success: #16803c;
    --warning: #a15c00;
    --danger: #b42318;
    --info: #0f6f84;
    --shadow: 0 14px 30px rgba(31, 42, 68, 0.08);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background: var(--bg);
    color: var(--ink);
}

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

.topbar {
    align-items: center;
    background: var(--panel);
    border-bottom: 1px solid var(--line);
    display: flex;
    gap: 24px;
    justify-content: space-between;
    min-height: 64px;
    padding: 0 28px;
    position: sticky;
    top: 0;
    z-index: 10;
}

.brand {
    color: var(--ink);
    font-size: 18px;
    font-weight: 800;
}

.nav {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    justify-content: flex-end;
}

.nav a {
    border-radius: 6px;
    color: var(--muted);
    font-weight: 700;
    padding: 9px 11px;
}

.nav a:hover,
.filter-tabs .active {
    background: #eaf1ff;
    color: var(--primary);
}

.page {
    margin: 0 auto;
    max-width: 1180px;
    padding: 28px;
}

.page-head,
.section-title,
.task-card-foot {
    align-items: center;
    display: flex;
    gap: 16px;
    justify-content: space-between;
}

.page-head {
    margin-bottom: 22px;
}

.eyebrow {
    color: var(--primary);
    font-size: 12px;
    font-weight: 800;
    letter-spacing: 0;
    margin: 0 0 6px;
    text-transform: uppercase;
}

h1,
h2,
h3,
p {
    margin-top: 0;
}

h1 {
    font-size: 34px;
    line-height: 1.15;
    margin-bottom: 0;
}

h2 {
    font-size: 21px;
}

h3 {
    font-size: 17px;
    margin-bottom: 8px;
}

.muted {
    color: var(--muted);
}

.small {
    font-size: 13px;
}

.card {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    box-shadow: var(--shadow);
    padding: 22px;
}

.auth-panel {
    align-items: center;
    display: grid;
    gap: 40px;
    grid-template-columns: minmax(0, 1fr) 380px;
    min-height: calc(100vh - 120px);
}

.narrow {
    margin: 40px auto;
    max-width: 560px;
}

.split {
    align-items: start;
    display: grid;
    gap: 22px;
    grid-template-columns: 360px minmax(0, 1fr);
}

.wide-left {
    grid-template-columns: 460px minmax(0, 1fr);
}

.full-width {
    display: block;
}

.form-card {
    display: grid;
    gap: 15px;
}

label {
    color: var(--ink);
    display: grid;
    font-size: 14px;
    font-weight: 800;
    gap: 7px;
}

input,
select,
textarea {
    border: 1px solid var(--line);
    border-radius: 7px;
    color: var(--ink);
    font: inherit;
    padding: 11px 12px;
    width: 100%;
}

textarea {
    resize: vertical;
}

input:focus,
select:focus,
textarea:focus,
.paste-zone:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.14);
    outline: none;
}

.field-grid,
.detail-grid {
    display: grid;
    gap: 13px;
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

.detail-grid {
    margin: 16px 0 22px;
}

.detail-grid span {
    background: #f7f9fc;
    border: 1px solid var(--line);
    border-radius: 7px;
    color: var(--muted);
    display: grid;
    gap: 5px;
    padding: 12px;
}

.detail-grid strong {
    color: var(--ink);
}

.btn {
    align-items: center;
    background: #eef2f7;
    border: 0;
    border-radius: 7px;
    color: var(--ink);
    cursor: pointer;
    display: inline-flex;
    font-weight: 800;
    justify-content: center;
    min-height: 42px;
    padding: 10px 15px;
}

.btn.primary {
    background: var(--primary);
    color: #fff;
}

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

.btn.small {
    min-height: 34px;
    padding: 7px 11px;
}

.button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.row-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    justify-content: flex-end;
}

.flash {
    border-radius: 7px;
    font-weight: 800;
    margin-bottom: 18px;
    padding: 13px 15px;
}

.flash.success {
    background: #eaf8ef;
    color: var(--success);
}

.flash.danger {
    background: #fff0ee;
    color: var(--danger);
}

.flash.warning {
    background: #fff7e8;
    color: var(--warning);
}

.stats-grid,
.student-task-grid {
    display: grid;
    gap: 16px;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    margin-bottom: 22px;
}

.stat {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    padding: 20px;
}

.stat span {
    display: block;
    font-size: 34px;
    font-weight: 800;
}

.stat p {
    color: var(--muted);
    margin: 4px 0 0;
}

.table-wrap {
    overflow-x: auto;
}

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

th,
td {
    border-bottom: 1px solid var(--line);
    padding: 13px 10px;
    text-align: left;
    vertical-align: top;
}

th {
    color: var(--muted);
    font-size: 12px;
    text-transform: uppercase;
}

.compact-card {
    padding: 16px;
}

.compact-table th,
.compact-table td {
    padding: 8px 9px;
}

.compact-table td {
    font-size: 14px;
}

.compact-table .btn.small {
    min-height: 30px;
    padding: 5px 9px;
}

.block {
    display: block;
    margin-top: 3px;
}

.mini-stats {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin: 0 0 12px;
}

.mini-stats span {
    background: #f7f9fc;
    border: 1px solid var(--line);
    border-radius: 7px;
    color: var(--muted);
    font-size: 13px;
    font-weight: 800;
    padding: 7px 10px;
}

.mini-stats strong {
    color: var(--ink);
}

.table-toolbar {
    align-items: end;
    display: grid;
    gap: 12px;
    grid-template-columns: minmax(220px, 1fr) 180px auto;
    margin-bottom: 12px;
}

.result-count {
    color: var(--muted);
    font-size: 13px;
    font-weight: 800;
    padding: 11px 0;
    white-space: nowrap;
}

.badge {
    border-radius: 999px;
    display: inline-flex;
    font-size: 12px;
    font-weight: 800;
    padding: 5px 9px;
}

.badge-muted {
    background: #eef2f7;
    color: #516070;
}

.badge-info {
    background: #e4f7fb;
    color: var(--info);
}

.badge-success {
    background: #eaf8ef;
    color: var(--success);
}

.badge-warning {
    background: #fff3df;
    color: var(--warning);
}

.task-list {
    display: grid;
    gap: 14px;
}

.task-row {
    border: 1px solid var(--line);
    border-radius: 8px;
    display: grid;
    gap: 16px;
    grid-template-columns: minmax(0, 1fr) 110px;
    padding: 16px;
}

.task-meta {
    align-items: center;
    color: var(--muted);
    display: flex;
    flex-wrap: wrap;
    font-size: 13px;
    gap: 8px;
    margin-bottom: 9px;
}

.task-progress {
    align-self: center;
    color: var(--muted);
    display: grid;
    justify-items: end;
}

.task-progress strong {
    color: var(--ink);
    font-size: 22px;
}

.student-task-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.task-card {
    display: grid;
    gap: 12px;
}

.progress-pill {
    background: #eaf1ff;
    border-radius: 999px;
    color: var(--primary);
    font-weight: 800;
    padding: 10px 14px;
}

.filter-tabs {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    padding: 5px;
}

.filter-tabs a {
    border-radius: 6px;
    color: var(--muted);
    font-weight: 800;
    padding: 8px 10px;
}

.submission-note,
.feedback {
    background: #f7f9fc;
    border: 1px solid var(--line);
    border-radius: 8px;
    margin-bottom: 12px;
    padding: 14px;
}

.screenshot-grid,
.preview-grid {
    display: grid;
    gap: 10px;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    margin-top: 12px;
}

.screenshot-grid img,
.preview-grid img {
    aspect-ratio: 4 / 3;
    border: 1px solid var(--line);
    border-radius: 7px;
    object-fit: cover;
    width: 100%;
}

.paste-zone {
    align-items: center;
    background: #f7f9fc;
    border: 2px dashed #b9c4d4;
    border-radius: 8px;
    color: var(--muted);
    display: flex;
    font-weight: 800;
    justify-content: center;
    min-height: 96px;
    padding: 16px;
    text-align: center;
}

.checkline {
    align-items: center;
    display: flex;
    flex-direction: row;
    gap: 10px;
}

.checkline input {
    width: auto;
}

.example-box {
    background: #f7f9fc;
    border: 1px solid var(--line);
    border-radius: 8px;
    margin-top: 14px;
    padding: 14px;
}

.example-box pre {
    color: var(--ink);
    font-family: Consolas, Monaco, monospace;
    font-size: 13px;
    line-height: 1.55;
    margin: 10px 0 0;
    overflow-x: auto;
    white-space: pre-wrap;
}

.empty {
    color: var(--muted);
    padding: 18px;
    text-align: center;
}

@media (max-width: 900px) {
    .auth-panel,
    .split,
    .wide-left,
    .table-toolbar,
    .stats-grid,
    .student-task-grid {
        grid-template-columns: 1fr;
    }

    .topbar,
    .page-head {
        align-items: flex-start;
        flex-direction: column;
    }

    .page {
        padding: 18px;
    }
}

@media (max-width: 560px) {
    h1 {
        font-size: 28px;
    }

    .field-grid,
    .detail-grid,
    .task-row,
    .screenshot-grid,
    .preview-grid {
        grid-template-columns: 1fr;
    }
}