:root {
  color-scheme: light;
  --bg: #f4f7fb;
  --card-bg: #ffffff;
  --text: #111827;
  --muted: #4b5563;
  --accent: #2563eb;
  --accent-press: #1d4ed8;
  --border: #dbe3ef;
  --exercise-bg: #f8fbff;
  --exercise-border: #d6e5ff;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: radial-gradient(circle at top, #e9f1ff 0%, var(--bg) 45%, #eef2f7 100%);
  color: var(--text);
}

.app {
  width: min(1100px, 100%);
  margin: 0 auto;
  min-height: 100vh;
  display: grid;
  grid-template-rows: auto 1fr auto;
  gap: clamp(14px, 2.2vh, 24px);
  padding: clamp(14px, 2.5vw, 28px);
}

.app__header {
  text-align: center;
}

.app__eyebrow {
  margin: 0;
  color: var(--muted);
  font-size: clamp(16px, 2.2vw, 24px);
}

.app__title {
  margin: 0.35em 0 0;
  font-size: clamp(28px, 5vw, 62px);
  line-height: 1.08;
}

.card {
  background: var(--card-bg);
  border: 2px solid var(--border);
  border-radius: 22px;
  padding: clamp(16px, 2.7vw, 30px);
  box-shadow: 0 12px 28px rgba(15, 23, 42, 0.08);
  overflow: auto;
}

.card__top {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 10px;
  background: linear-gradient(90deg, #f5f9ff 0%, #ffffff 100%);
  border: 1px solid #e3edfd;
  border-radius: 14px;
  padding: clamp(10px, 1.5vw, 14px);
}

.card__stage-label,
.card__counter {
  margin: 0;
  color: var(--muted);
  font-size: clamp(15px, 2vw, 22px);
}

.card__title {
  margin: 0.2em 0 0.45em;
  font-size: clamp(30px, 5.8vw, 72px);
  line-height: 1.04;
}

.card__description {
  margin: 0;
  font-size: clamp(20px, 2.8vw, 34px);
  line-height: 1.32;
}

.card__exercise-counter {
  margin: 0.6em 0 0;
  color: #1e40af;
  font-size: clamp(16px, 2vw, 26px);
  font-weight: 700;
}

.exercise-grid {
  margin-top: clamp(16px, 2.7vh, 28px);
  display: grid;
  gap: clamp(8px, 1.7vh, 14px);
}

.exercise {
  border: 1px solid var(--exercise-border);
  background: var(--exercise-bg);
  border-radius: 16px;
  padding: clamp(12px, 1.8vw, 18px);
}

.stage-card {
  border: 1px solid var(--exercise-border);
  background: var(--exercise-bg);
  border-radius: 16px;
  padding: clamp(12px, 1.8vw, 18px);
  display: grid;
  gap: 8px;
}

.stage-card--completion {
  border: 2px solid #74d39b;
  background: linear-gradient(180deg, #f4fff8 0%, #e8f8ef 100%);
  padding: clamp(18px, 2.5vw, 28px);
  box-shadow: 0 14px 24px rgba(34, 139, 86, 0.14);
}

.stage-card--completion .stage-card__title {
  font-size: clamp(28px, 3.8vw, 48px);
  line-height: 1.12;
}

.stage-card--completion .stage-card__desc {
  font-size: clamp(20px, 2.6vw, 34px);
  line-height: 1.26;
}

.stage-card__badge {
  margin: 0;
  justify-self: start;
  background: #1f9d63;
  color: #ffffff;
  border-radius: 999px;
  padding: 8px 14px;
  font-size: clamp(14px, 1.7vw, 20px);
  font-weight: 800;
  letter-spacing: 0.02em;
}

.stage-card__title {
  margin: 0;
  font-size: clamp(20px, 2.4vw, 30px);
  line-height: 1.2;
}

.stage-card__meta {
  margin: 0;
  color: #1e40af;
  font-size: clamp(16px, 1.9vw, 24px);
  font-weight: 700;
}

.stage-card__desc {
  margin: 0;
  font-size: clamp(17px, 2vw, 27px);
  line-height: 1.25;
}

.stage-card__btn {
  justify-self: start;
  border: 0;
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  padding: 10px 14px;
  font-size: clamp(15px, 1.8vw, 22px);
  cursor: pointer;
}

.stage-card__btn:hover {
  background: var(--accent-press);
}

.exercise__title {
  margin: 0;
  font-size: clamp(20px, 2.4vw, 30px);
  line-height: 1.2;
}

.exercise__meta {
  margin: 0.35em 0 0;
  color: #1e3a8a;
  font-size: clamp(16px, 1.9vw, 24px);
  font-weight: 700;
}

.exercise__how {
  margin: 0.4em 0 0;
  font-size: clamp(17px, 2vw, 27px);
  line-height: 1.28;
}

.card__note {
  margin-top: clamp(16px, 2.6vh, 26px);
  padding: clamp(12px, 1.6vw, 18px);
  border-radius: 14px;
  background: #f7f9fc;
  border: 1px solid #e5ebf5;
  font-size: clamp(17px, 2vw, 28px);
  line-height: 1.3;
  color: #1f2937;
}

.controls {
  display: flex;
  gap: clamp(10px, 1.8vw, 16px);
}

.btn {
  flex: 1;
  border: 0;
  border-radius: 14px;
  padding: clamp(12px, 1.8vh, 18px);
  font-size: clamp(20px, 2.2vw, 30px);
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.08s ease, background-color 0.2s ease, opacity 0.2s ease;
}

.btn:active {
  transform: scale(0.99);
}

.btn:disabled {
  opacity: 0.45;
  cursor: default;
  transform: none;
}

.btn[hidden] {
  display: none;
}

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

.btn--primary:hover:not(:disabled) {
  background: var(--accent-press);
}

.btn--secondary {
  background: #e7edf6;
  color: #0f172a;
}

@media (max-width: 720px) {
  .controls {
    position: sticky;
    bottom: 0;
    padding-bottom: 2px;
  }

  .card {
    border-radius: 18px;
  }
}