:root {
  --bg: #f6f7fb;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --blue: #2563eb;
  --green: #16a34a;
  --red: #dc2626;
  --border: rgba(17, 24, 39, 0.10);
  --shadow: 0 12px 30px rgba(17, 24, 39, 0.10);
  --radius: 18px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
  background: var(--bg);
  color: var(--text);
}

.app {
  max-width: 560px;
  margin: 0 auto;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  position: sticky;
  top: 0;
  background: rgba(246,247,251,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 14px 16px;
  z-index: 5;
}

.nav {
  display: flex;
  align-items: center;
  gap: 10px;
}

.back-btn {
  display: none;
  appearance: none;
  border: 0;
  background: rgba(37,99,235,0.10);
  padding: 8px 10px;
  border-radius: 12px;
  color: var(--blue);
  font-weight: 800;
  cursor: pointer;
}

.title {
  font-size: 18px;
  font-weight: 800;
  letter-spacing: 0.2px;
}

main {
  padding: 18px 16px 24px;
  flex: 1;
}

.hero {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
}

.hero-left h1 {
  margin: 0 0 6px;
  font-size: 26px;
  line-height: 1.15;
}

.hero-left p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.4;
}

.logo {
  width: 58px;
  height: 58px;
  border-radius: 16px;
  background: linear-gradient(135deg, #93c5fd, #2563eb);
  box-shadow: var(--shadow);
  display: grid;
  place-items: center;
  color: white;
  font-weight: 900;
  letter-spacing: 0.05em;
}

.list {
  display: grid;
  gap: 12px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 14px;
}

.cat-btn {
  width: 100%;
  text-align: left;
  border: 0;
  background: transparent;
  padding: 0;
  cursor: pointer;
}

.cat-row {
  display: flex;
  gap: 12px;
  align-items: center;
}

.icon {
  width: 44px;
  height: 44px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  background: rgba(37, 99, 235, 0.12);
  font-size: 18px;
  flex: 0 0 auto;
}

.cat-title {
  font-size: 16px;
  font-weight: 800;
  margin: 0 0 4px;
}

.cat-sub {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.35;
}

.label {
  color: var(--muted);
  font-size: 12px;
  font-weight: 800;
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.question-text {
  font-size: 18px;
  line-height: 1.35;
  margin: 0 0 14px;
}

.input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 12px 12px;
  font-size: 16px;
  outline: none;
  background: #fff;
}

.input:focus {
  border-color: rgba(37,99,235,0.45);
  box-shadow: 0 0 0 4px rgba(37,99,235,0.12);
}

.row {
  display: grid;
  gap: 10px;
  margin-top: 12px;
}

.btn {
  width: 100%;
  border: 0;
  border-radius: 14px;
  padding: 12px 14px;
  font-size: 16px;
  font-weight: 900;
  cursor: pointer;
}

.btn-primary { background: var(--blue); color: white; }
.btn-secondary { background: rgba(17,24,39,0.08); color: var(--text); }

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.result {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
}

.result-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.correct-line {
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
  text-align: right;
}

.pill {
  display: inline-block;
  padding: 6px 10px;
  border-radius: 999px;
  font-weight: 900;
  font-size: 13px;
}

.pill.ok { background: rgba(22,163,74,0.12); color: var(--green); }
.pill.bad { background: rgba(220,38,38,0.12); color: var(--red); }

.explain {
  margin-top: 10px;
  color: var(--text);
  line-height: 1.45;
  white-space: pre-wrap;
}

.muted {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.45;
}

footer {
  padding: 10px 16px 18px;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.4;
}

.hidden { display: none !important; }