:root {
  --bg: #f5f7fb;
  --panel: #ffffff;
  --text: #1a2333;
  --muted: #5f6e85;
  --accent: #0e7a6a;
  --accent-strong: #0a6154;
  --line: #d9e0ec;
  --danger: #b3261e;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--text);
  background: radial-gradient(circle at top right, #eef7f5 0, #f5f7fb 45%, #f5f7fb 100%);
  font-family: "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
}

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 24px 16px 40px;
}

.page-header h1 {
  margin: 8px 0 10px;
  font-size: 30px;
}

.page-header p {
  margin: 0;
  color: var(--muted);
}

.panel {
  margin-top: 18px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--panel);
}

.panel h2 {
  margin: 0 0 12px;
  font-size: 20px;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 16px;
  margin-top: 20px;
}

.card {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--panel);
  padding: 16px;
}

.card h2 {
  margin: 0 0 8px;
}

.card p {
  margin: 0 0 14px;
  color: var(--muted);
}

.button {
  border: 0;
  border-radius: 8px;
  padding: 8px 12px;
  color: #fff;
  background: var(--accent);
  cursor: pointer;
  font-size: 14px;
  line-height: 1.3;
  text-decoration: none;
  display: inline-block;
}

.button:hover {
  background: var(--accent-strong);
}

.button-secondary {
  background: #2f4b7a;
}

.button-secondary:hover {
  background: #213b66;
}

.button-ghost {
  background: #e7edf7;
  color: #24364f;
}

.button-ghost:hover {
  background: #d6e1f0;
}

.link {
  color: var(--accent);
  text-decoration: none;
}

.link:hover {
  text-decoration: underline;
}

.controls-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 12px;
  margin-bottom: 12px;
  align-items: center;
}

label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
}

select {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 6px 8px;
  background: #fff;
  color: var(--text);
}

.status {
  margin: 8px 0;
  color: var(--muted);
}

.status-error {
  color: var(--danger);
}

.media-player {
  width: 100%;
  max-height: 360px;
  border-radius: 10px;
  margin-top: 8px;
  background: #e9eef8;
}

.grade-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 12px;
}

.grade-tab.active {
  background: #0a6154;
  color: #fff;
}

.track-list {
  margin: 0;
  padding-left: 22px;
}

.track-list li {
  margin-bottom: 8px;
}

.track-btn {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  padding: 9px 10px;
  color: var(--text);
  text-align: left;
  cursor: pointer;
}

.track-btn:hover {
  border-color: #9db5d8;
  background: #f4f8ff;
}

.track-btn.active {
  border-color: #0e7a6a;
  background: #ecfaf7;
}

@media (max-width: 700px) {
  .page-header h1 {
    font-size: 24px;
  }
}