:root {
    --ink: #1f2933;
    --muted: #6b7280;
    --line: #e5e7eb;
    --bg: #f6f7f9;
    --card: #ffffff;
    --accent: #2563eb;
    --accent-dark: #1d4ed8;
    --ok: #15803d;
    --warn: #b45309;
    --err: #b91c1c;
}
* { box-sizing: border-box; }
body {
    margin: 0; background: var(--bg); color: var(--ink);
    font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
    font-size: 16px; line-height: 1.6;
}
.container { max-width: 760px; margin: 0 auto; padding: 16px; }
.topbar {
    background: var(--card); border-bottom: 1px solid var(--line);
    padding: 12px 16px; display: flex; align-items: center; gap: 12px;
    position: sticky; top: 0; z-index: 10;
}
.topbar .brand { font-weight: 700; font-size: 17px; }
.topbar .spacer { flex: 1; }
.topbar a { color: var(--accent); text-decoration: none; font-size: 14px; }
.card {
    background: var(--card); border: 1px solid var(--line);
    border-radius: 10px; padding: 16px; margin-bottom: 14px;
}
h1 { font-size: 22px; margin: 8px 0 16px; }
h2 { font-size: 18px; margin: 4px 0 12px; }
.muted { color: var(--muted); font-size: 14px; }
label { display: block; font-size: 14px; font-weight: 600; margin: 12px 0 4px; }
input[type=text], input[type=password], input[type=number], select, textarea {
    width: 100%; padding: 10px 12px; border: 1px solid var(--line);
    border-radius: 8px; font-size: 16px; font-family: inherit; background: #fff;
}
textarea { min-height: 160px; resize: vertical; }
.btn {
    display: inline-block; padding: 11px 20px; border: none; border-radius: 8px;
    background: var(--accent); color: #fff; font-size: 16px; cursor: pointer;
    text-decoration: none; text-align: center; margin-top: 14px;
}
.btn:hover { background: var(--accent-dark); }
.btn.secondary { background: #fff; color: var(--ink); border: 1px solid var(--line); }
.btn.small { padding: 6px 12px; font-size: 14px; margin-top: 0; }
.flash-ok { background: #ecfdf5; color: var(--ok); border: 1px solid #a7f3d0; border-radius: 8px; padding: 10px 14px; margin-bottom: 12px; }
.flash-error { background: #fef2f2; color: var(--err); border: 1px solid #fecaca; border-radius: 8px; padding: 10px 14px; margin-bottom: 12px; }
.tag {
    display: inline-block; font-size: 12px; padding: 2px 8px; border-radius: 999px;
    background: #eef2ff; color: var(--accent-dark); margin-right: 6px;
}
.tag.pending { background: #fffbeb; color: var(--warn); }
.tag.published { background: #ecfdf5; color: var(--ok); }
.tag.grading { background: #eff6ff; color: var(--accent); }
.tag.failed { background: #fef2f2; color: var(--err); }
table { width: 100%; border-collapse: collapse; font-size: 15px; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line); }
th { color: var(--muted); font-weight: 600; font-size: 13px; }
.feedback {
    white-space: pre-wrap; word-break: break-word; font-size: 15px;
    background: #fbfcfe; border: 1px solid var(--line); border-radius: 8px; padding: 14px;
}
.score-big { font-size: 34px; font-weight: 700; color: var(--accent-dark); }
.ai-note {
    background: #fffbeb; border: 1px solid #fde68a; color: #92400e;
    border-radius: 8px; padding: 10px 14px; margin: 4px 0 14px; font-size: 14px;
}
.essay-img { max-width: 100%; border: 1px solid var(--line); border-radius: 8px; cursor: zoom-in; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.progress-note { font-size: 14px; color: var(--muted); }
a { color: var(--accent); }
.list-item { display: block; text-decoration: none; color: var(--ink); }
.list-item:hover { border-color: var(--accent); }
.spinner {
    display: inline-block; width: 16px; height: 16px; border: 2px solid var(--line);
    border-top-color: var(--accent); border-radius: 50%;
    animation: spin 0.8s linear infinite; vertical-align: -3px;
}
@keyframes spin { to { transform: rotate(360deg); } }
@media (max-width: 600px) {
    .container { padding: 12px; }
    h1 { font-size: 20px; }
    .btn { width: 100%; }
}