:root {
  --bg-primary:    #1a1a1a;
  --bg-card:       #242424;
  --bg-hover:      #2e2e2e;
  --bg-input:      #333333;
  --salmon:        #FA8072;
  --salmon-light:  #FFA69E;
  --salmon-muted:  #e8735f;
  --salmon-bg:     rgba(250, 128, 114, 0.08);
  --text-primary:  #f0f0f0;
  --text-secondary:#a0a0a0;
  --text-muted:    #666666;
  --correct:       #4ade80;
  --correct-bg:    rgba(74, 222, 128, 0.1);
  --incorrect:     #f87171;
  --incorrect-bg:  rgba(248, 113, 113, 0.1);
  --border:        rgba(255,255,255,0.08);
  --border-hover:  rgba(255,255,255,0.15);
  --font:          'Inter', system-ui, -apple-system, sans-serif;
  --radius:        8px;
  --radius-lg:     12px;
  --transition:    0.2s ease;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: var(--font);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}
a { color: var(--salmon); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Layout */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
}
.brand { font-weight: bold; font-size: 1.25rem; color: var(--salmon); }
main { max-width: 800px; margin: 0 auto; padding: 2rem; }

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1rem;
  transition: var(--transition);
}
.card.clickable:hover {
  border-color: var(--salmon);
  transform: translateY(-2px);
  cursor: pointer;
}
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1rem; }

/* Buttons */
button {
  background: var(--salmon);
  color: #000;
  border: none;
  border-radius: var(--radius);
  padding: 0.5rem 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: var(--transition);
}
button:hover { background: var(--salmon-light); }
button.secondary {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border);
}
button.secondary:hover { background: var(--bg-hover); }

/* Forms */
.form-group { margin-bottom: 1rem; }
label { display: block; margin-bottom: 0.5rem; font-size: 0.9rem; color: var(--text-secondary); }
input[type="email"], input[type="password"] {
  width: 100%;
  padding: 0.75rem;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text-primary);
}
input:focus { outline: none; border-color: var(--salmon); }

/* Exam Interface */
.top-bar {
  position: sticky; top: 0; z-index: 10;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 2rem;
  display: flex; justify-content: space-between; align-items: center;
}
.timer { font-family: monospace; font-size: 1.25rem; font-weight: bold; }
.timer.danger { color: var(--incorrect); animation: pulse 1s infinite; }

.bottom-bar {
  position: fixed; bottom: 0; left: 0; right: 0; z-index: 10;
  background: var(--bg-card);
  border-top: 1px solid var(--border);
  padding: 1rem 2rem;
  display: flex; gap: 1rem; align-items: center; justify-content: space-between;
}
.navigator { display: flex; gap: 0.5rem; overflow-x: auto; flex: 1; padding: 0.5rem; align-items: center; }
.nav-dot {
  min-width: 32px; height: 32px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  background: var(--bg-input); font-size: 0.8rem; cursor: pointer;
  border: 2px solid transparent; position: relative;
}
.nav-dot.answered { background: var(--salmon); color: #000; font-weight: bold; }
.nav-dot.current { border-color: var(--salmon); background: var(--bg-card); color: var(--text-primary); transform: scale(1.1); }
.nav-dot.revealed::after {
  content: ''; position: absolute; bottom: -6px; width: 4px; height: 4px; border-radius: 50%; background: var(--salmon);
}

.options-list { margin-top: 1.5rem; display: flex; flex-direction: column; gap: 0.75rem; }
.option {
  display: flex; gap: 1rem; padding: 1rem; border: 1px solid var(--border);
  border-radius: var(--radius); cursor: pointer; transition: var(--transition);
}
.option:hover { background: var(--bg-hover); }
.option.selected { border-color: var(--salmon); background: var(--salmon-bg); }
.option.correct { border-color: var(--correct); background: var(--correct-bg); }
.option.incorrect { border-color: var(--incorrect); background: var(--incorrect-bg); }
.option input { margin-top: 4px; }

.explanation { margin-top: 2rem; padding: 1.5rem; border-radius: var(--radius); background: var(--bg-card); border-left: 4px solid var(--salmon); }
.explanation h4 { margin-bottom: 0.5rem; margin-top: 1rem; }
.explanation img { max-width: 100%; border-radius: var(--radius); margin-top: 1rem; }
.stem img { max-width: 100%; border-radius: var(--radius); margin: 1rem 0; }

/* Utilities */
.hidden { display: none !important; }
@keyframes pulse { 50% { opacity: 0.5; } }
#toast {
  position: fixed; bottom: 80px; right: 20px;
  background: var(--salmon); color: #000; padding: 0.75rem 1.5rem;
  border-radius: var(--radius); font-weight: bold;
  opacity: 0; transition: opacity 0.3s; pointer-events: none;
}
#toast.show { opacity: 1; }

.modal-overlay {
  position: fixed; top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0,0,0,0.7); display: flex; align-items: center; justify-content: center; z-index: 100;
}
.modal { background: var(--bg-card); padding: 2rem; border-radius: var(--radius-lg); width: 100%; max-width: 400px; }

/* Mobile Responsiveness */
@media (max-width: 600px) {
  header { padding: 1rem; }
  main { padding: 1rem; }
  
  #user-email { display: none; }
  
  .top-bar {
    padding: 0.75rem 1rem;
    flex-direction: column;
    align-items: stretch;
    gap: 0.75rem;
  }
  .top-bar > div {
    width: 100%;
    justify-content: space-between;
    gap: 0.5rem !important;
  }
  .top-bar button {
    padding: 0.5rem;
    font-size: 0.8rem !important;
    flex: 1;
  }
  
  .timer { font-size: 1rem; }
  
  .bottom-bar {
    padding: 0.75rem 1rem;
    gap: 0.5rem;
  }
  .bottom-bar button {
    padding: 0.5rem;
    font-size: 0.8rem;
  }
  
  .navigator { padding: 0; }
  .nav-dot { min-width: 28px; height: 28px; font-size: 0.7rem; }
}