*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f1f5f9;
  color: #1e293b;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 2rem 1rem;
}

.app {
  width: 100%;
  max-width: 640px;
}

/* ── Login screen ───────────────────────────────────────────────────── */

#login-screen:not([hidden]) {
  display: flex;
  align-items: center;
  justify-content: center;
}

.login-card {
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.08);
  padding: 2.5rem 2rem;
  width: 100%;
  max-width: 400px;
}

.login-card h1 { margin-bottom: 0.4rem; }

.login-subtitle {
  color: #64748b;
  font-size: 0.9rem;
  margin-bottom: 1.75rem;
}

.login-card label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: #475569;
  margin-bottom: 0.4rem;
}

.login-card input {
  width: 100%;
  padding: 0.65rem 0.9rem;
  border: 2px solid #e2e8f0;
  border-radius: 10px;
  font-size: 1rem;
  color: #1e293b;
  margin-bottom: 0.75rem;
  outline: none;
  transition: border-color 0.15s;
}

.login-card input:focus { border-color: #3b82f6; }

.login-card > div > button {
  width: 100%;
  padding: 0.7rem;
  background: #3b82f6;
  color: #fff;
  border: none;
  border-radius: 10px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}

.login-card > div > button:hover { background: #2563eb; }

.login-error {
  color: #dc2626;
  font-size: 0.85rem;
  margin-top: 0.5rem;
}

.login-hint {
  font-size: 0.9rem;
  color: #475569;
  margin-bottom: 0.75rem;
}

/* ── Quiz screen header ─────────────────────────────────────────────── */

header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 1.5rem;
  gap: 1rem;
}

h1 {
  font-size: 1.4rem;
  font-weight: 700;
  color: #3b82f6;
}

.header-right {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.35rem;
}

.score-box {
  font-size: 0.95rem;
  font-weight: 600;
  color: #64748b;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8rem;
  color: #64748b;
}

.progress-badge {
  background: #eff6ff;
  color: #3b82f6;
  padding: 0.1rem 0.5rem;
  border-radius: 99px;
  font-size: 0.75rem;
  font-weight: 600;
}

.header-actions { display: flex; gap: 0.5rem; }

.btn-ghost {
  background: none;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  font-size: 0.8rem;
  color: #64748b;
  padding: 0.3rem 0.65rem;
  cursor: pointer;
  white-space: nowrap;
  transition: border-color 0.15s, color 0.15s;
}

.btn-ghost:hover { border-color: #94a3b8; color: #334155; }

/* ── Card ───────────────────────────────────────────────────────────── */

.card {
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.08);
  padding: 2rem;
  margin-bottom: 1rem;
}

.sentence {
  font-size: 1.15rem;
  line-height: 1.8;
  margin-bottom: 1.75rem;
  color: #1e293b;
}

.blank {
  display: inline-block;
  min-width: 7rem;
  border-bottom: 2.5px solid #3b82f6;
  text-align: center;
  font-weight: 600;
  color: #3b82f6;
  padding: 0 0.25rem;
  margin: 0 0.15rem;
  transition: color 0.2s, border-color 0.2s;
}

.blank.filled-correct  { color: #16a34a; border-color: #16a34a; }
.blank.filled-incorrect { color: #dc2626; border-color: #dc2626; }

.choices {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.choice-btn {
  padding: 0.75rem 1rem;
  border: 2px solid #e2e8f0;
  border-radius: 10px;
  background: #f8fafc;
  font-size: 1rem;
  font-weight: 500;
  color: #334155;
  cursor: pointer;
  text-align: center;
  transition: border-color 0.15s, background 0.15s, color 0.15s;
}

.choice-btn:hover:not(:disabled) {
  border-color: #3b82f6;
  background: #eff6ff;
  color: #1d4ed8;
}

.choice-btn:disabled { cursor: default; }

.choice-btn.correct  { border-color: #16a34a; background: #f0fdf4; color: #15803d; }
.choice-btn.incorrect { border-color: #dc2626; background: #fef2f2; color: #b91c1c; }

.meta {
  font-size: 0.8rem;
  color: #94a3b8;
  text-align: right;
}

.actions {
  display: flex;
  justify-content: flex-end;
}

#next-btn {
  padding: 0.7rem 1.5rem;
  background: #3b82f6;
  color: #fff;
  border: none;
  border-radius: 10px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, opacity 0.15s;
}

#next-btn:hover:not(:disabled) { background: #2563eb; }
#next-btn:disabled { opacity: 0.35; cursor: default; }

.loading {
  display: block;
  text-align: center;
  color: #94a3b8;
  font-size: 1rem;
  padding: 2rem 0;
}

.all-done {
  text-align: center;
  font-size: 1.1rem;
  font-weight: 600;
  color: #16a34a;
  padding: 2rem 0;
}