/* ── Page wrapper ───────────────────────────────────────────── */
.physics-page {
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 20px 60px;
}

/* ── Header ─────────────────────────────────────────────────── */
.physics-back-link {
  display: inline-block;
  font-size: 14px;
  color: var(--color-text-muted);
  text-decoration: none;
  margin-bottom: 16px;
  transition: color 0.15s;
}
.physics-back-link:hover { color: var(--color-action); text-decoration: none; }

.physics-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-text-dark);
  margin-bottom: 6px;
}

.physics-subtitle {
  font-size: 15px;
  color: var(--color-text-muted);
  margin-bottom: 40px;
}

/* ── Level block ────────────────────────────────────────────── */
.physics-level {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px 24px 20px;
  box-shadow: var(--shadow-sm);
}

.physics-level-header {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  margin-bottom: 18px;
}

.physics-level-badge {
  flex-shrink: 0;
  background: var(--color-action-gradient);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  margin-top: 3px;
}

.physics-level-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--color-text-dark);
  margin-bottom: 2px;
}

.physics-level-desc {
  font-size: 13px;
  color: var(--color-text-muted);
}

/* ── Connector between levels ───────────────────────────────── */
.physics-level-connector {
  width: 2px;
  height: 28px;
  background: var(--color-border);
  margin: 0 auto;
}

/* ── Subject cards ──────────────────────────────────────────── */
.physics-subjects {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.physics-subject-card {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 14px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  background: var(--color-background);
  transition: box-shadow 0.15s, border-color 0.15s;
  text-decoration: none;
  color: inherit;
  position: relative;
  overflow: hidden;
}

/* green fill overlay driven by --pct CSS variable */
.physics-subject-card--progress::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg,
    rgba(16, 185, 129, 0.10) var(--pct, 0%),
    transparent var(--pct, 0%)
  );
  pointer-events: none;
  border-radius: inherit;
  transition: background 0.4s ease;
}

.subject-progress-badge {
  flex-shrink: 0;
  font-size: 11px;
  font-weight: 700;
  color: #10b981;
  background: rgba(16, 185, 129, 0.12);
  padding: 3px 8px;
  border-radius: var(--radius-full);
  z-index: 1;
}

.subject-progress-badge--done {
  color: #fff;
  background: var(--color-action-gradient);
}

.physics-subject-card--link {
  cursor: pointer;
}
.physics-subject-card--link:hover {
  border-color: var(--color-action);
  box-shadow: var(--shadow-base);
  text-decoration: none;
  color: inherit;
}

.physics-subject-card--soon {
  opacity: 0.6;
  cursor: default;
}

.physics-subject-icon {
  font-size: 1.8rem;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  background: var(--color-surface);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
}

.physics-subject-body {
  flex: 1;
  min-width: 0;
}

.physics-subject-name {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text-dark);
  margin-bottom: 2px;
}

.physics-subject-desc {
  font-size: 13px;
  color: var(--color-text-muted);
}

/* ── Prerequisites ──────────────────────────────────────────── */
.physics-prereqs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  margin-top: 8px;
}

.physics-prereqs-label {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-right: 2px;
}

.physics-prereq-tag {
  font-size: 12px;
  font-weight: 500;
  color: var(--color-text-muted);
  background: var(--color-hover-gray);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  padding: 2px 10px;
  text-decoration: none;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}

.physics-prereq-tag--link {
  color: var(--color-action);
  border-color: var(--color-action);
  background: transparent;
}
.physics-prereq-tag--link:hover {
  background: var(--color-action);
  color: #fff;
  text-decoration: none;
}

/* ── Coming soon badge ──────────────────────────────────────── */
.physics-subject-soon-badge {
  flex-shrink: 0;
  font-size: 11px;
  font-weight: 600;
  color: var(--color-text-muted);
  background: var(--color-hover-gray);
  padding: 3px 9px;
  border-radius: var(--radius-full);
}