:root {
  color-scheme: light;
  --bg: #f4f7fb;
  --card: #ffffff;
  --text: #172033;
  --muted: #667085;
  --line: #d9e2ef;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --success: #10845b;
  --danger: #c2410c;
  --soft-blue: #eaf1ff;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(circle at top left, #dce9ff 0, transparent 32rem), var(--bg);
  color: var(--text);
}

.app-shell {
  width: min(920px, calc(100% - 32px));
  margin: 0 auto;
  padding: 56px 0;
}

.hero { margin-bottom: 24px; }

.eyebrow {
  margin: 0 0 8px;
  color: var(--primary);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

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

h1 {
  margin-bottom: 12px;
  font-size: clamp(2rem, 6vw, 4rem);
  line-height: 1.05;
  letter-spacing: -0.05em;
}

h2 { font-size: 1.1rem; }

.intro {
  max-width: 680px;
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.65;
}

.card {
  margin: 16px 0;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.88);
  box-shadow: 0 18px 45px rgba(31, 41, 55, 0.08);
}

.progress-card { display: grid; gap: 14px; }

.progress-copy {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
}

.progress-copy strong { color: var(--text); }

.progress-track {
  height: 12px;
  overflow: hidden;
  border-radius: 999px;
  background: #e6edf7;
}

.progress-bar {
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--primary), #60a5fa);
  transition: width 180ms ease;
}

.lesson-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}

.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 92px;
  padding: 10px 14px;
  border-radius: 16px;
  background: var(--soft-blue);
  color: var(--primary-dark);
  font-weight: 900;
  font-size: 1.15rem;
}

.lesson-title { font-size: 1.35rem; font-weight: 800; }
.lesson-description { font-size: 1.12rem; line-height: 1.7; }
.lesson-example { color: var(--muted); line-height: 1.65; }

.practice-card { display: grid; gap: 14px; }
.practice-prompt { color: var(--muted); line-height: 1.6; }
.system-note {
  margin: 0;
  padding: 12px 14px;
  border-radius: 14px;
  background: #fff7ed;
  color: #9a3412;
  font-weight: 700;
  line-height: 1.55;
}

.practice-area {
  display: grid;
  place-items: center;
  min-height: 148px;
  padding: 24px;
  border: 2px dashed #9db6df;
  border-radius: 20px;
  background: #f8fbff;
  color: var(--muted);
  font-weight: 700;
  text-align: center;
  outline: none;
  cursor: default;
}

.practice-area:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 5px rgba(37, 99, 235, 0.14);
  color: var(--text);
}

.practice-icon { display: block; margin-bottom: 8px; font-size: 2rem; }

.feedback {
  min-height: 1.5em;
  margin-bottom: 0;
  font-weight: 800;
}
.feedback.success { color: var(--success); }
.feedback.error { color: var(--danger); }

.primary-button,
.secondary-button {
  justify-self: start;
  border: 0;
  border-radius: 999px;
  padding: 12px 18px;
  background: #172033;
  color: white;
  font-weight: 800;
  cursor: pointer;
}

.primary-button { background: var(--primary); }
.primary-button:hover { background: var(--primary-dark); }
.secondary-button:hover { background: #0f172a; }

.shortcut-list ol, .shortcut-list li { margin-top: 0; }
#shortcutList { display: grid; gap: 8px; padding-left: 24px; color: var(--muted); }
#shortcutList strong { color: var(--text); }

@media (max-width: 640px) {
  .app-shell { width: min(100% - 20px, 920px); padding: 32px 0; }
  .card { padding: 18px; border-radius: 18px; }
  .progress-copy { display: grid; }
}