:root {
  --bg: #0f172a;
  --card: #1e293b;
  --primary: #38bdf8;
  --primary-dark: #0ea5e9;
  --success: #4ade80;
  --error: #f87171;
  --warning: #fbbf24;
  --text: #f1f5f9;
  --muted: #94a3b8;
  --letter-bg: #334155;
  --letter-hover: #475569;
  --slot-bg: #0f172a;
  --radius: 16px;
  --shadow: 0 10px 40px rgba(0, 0, 0, 0.4);
}

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

body {
  font-family: 'Nunito', system-ui, sans-serif;
  background: linear-gradient(145deg, #0f172a 0%, #1e1b4b 50%, #0f172a 100%);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
}

.app {
  max-width: 640px;
  margin: 0 auto;
  padding: 1.25rem;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  background: linear-gradient(90deg, #38bdf8, #a78bfa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.controls {
  display: flex;
  gap: 0.5rem;
}

select {
  background: var(--card);
  color: var(--text);
  border: 1px solid #334155;
  border-radius: 10px;
  padding: 0.5rem 0.75rem;
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  outline: none;
  transition: border-color 0.2s;
}

select:hover, select:focus {
  border-color: var(--primary);
}

/* Screens */
.screen {
  display: none;
  animation: fadeIn 0.3s ease;
}

.screen.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Cards */
.card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow);
  text-align: center;
}

.hero h2 {
  font-size: 1.6rem;
  margin-bottom: 0.75rem;
}

.hero p {
  color: var(--muted);
  margin-bottom: 1.5rem;
}

/* Stats preview */
.stats-preview {
  display: flex;
  gap: 1rem;
  margin-top: 1.5rem;
}

.stat {
  flex: 1;
  background: var(--card);
  border-radius: var(--radius);
  padding: 1.25rem;
  text-align: center;
  box-shadow: var(--shadow);
}

.stat-value {
  display: block;
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--primary);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--muted);
}

/* Game header */
.game-header {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.score-box, .progress-box, .timer-box {
  flex: 1;
  background: var(--card);
  border-radius: 12px;
  padding: 0.75rem;
  text-align: center;
}

.label {
  display: block;
  font-size: 0.75rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.value {
  font-size: 1.4rem;
  font-weight: 700;
}

/* Letters */
.letters-area {
  margin-bottom: 1.5rem;
}

.hint {
  text-align: center;
  color: var(--muted);
  margin-bottom: 0.75rem;
  font-size: 0.95rem;
}

.letters {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem;
  min-height: 60px;
}

.letter {
  width: 52px;
  height: 52px;
  background: var(--letter-bg);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 700;
  cursor: pointer;
  user-select: none;
  transition: transform 0.15s, background 0.15s, opacity 0.2s;
  box-shadow: 0 4px 0 #1e293b;
}

.letter:hover:not(.used) {
  background: var(--letter-hover);
  transform: translateY(-2px);
}

.letter:active:not(.used) {
  transform: translateY(2px);
  box-shadow: none;
}

.letter.used {
  opacity: 0.25;
  cursor: default;
  pointer-events: none;
}

/* Answer slots */
.answer-area {
  margin-bottom: 1.5rem;
}

.slots {
  display: flex;
  justify-content: center;
  gap: 0.4rem;
  margin-bottom: 1rem;
  min-height: 56px;
}

.slot {
  width: 48px;
  height: 52px;
  background: var(--slot-bg);
  border: 2px dashed #334155;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  font-weight: 700;
  transition: border-color 0.2s, background 0.2s;
}

.slot.filled {
  border-style: solid;
  border-color: var(--primary);
  background: #0c4a6e;
}

.slot.correct {
  border-color: var(--success);
  background: #14532d;
  animation: pop 0.3s ease;
}

.slot.wrong {
  border-color: var(--error);
  background: #450a0a;
  animation: shake 0.4s ease;
}

@keyframes pop {
  0% { transform: scale(1); }
  50% { transform: scale(1.15); }
  100% { transform: scale(1); }
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-6px); }
  40%, 80% { transform: translateX(6px); }
}

.answer-input {
  width: 100%;
  background: var(--card);
  border: 2px solid #334155;
  border-radius: 12px;
  padding: 0.85rem 1rem;
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text);
  text-align: center;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.answer-input:focus {
  border-color: var(--primary);
}

/* Buttons */
.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  justify-content: center;
  margin-bottom: 1rem;
}

.btn {
  border: none;
  border-radius: 12px;
  padding: 0.75rem 1.25rem;
  font-family: inherit;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.15s, background 0.2s, opacity 0.2s;
}

.btn:active {
  transform: scale(0.97);
}

.btn.primary {
  background: linear-gradient(135deg, var(--primary), #818cf8);
  color: #0f172a;
}

.btn.primary:hover {
  filter: brightness(1.1);
}

.btn.secondary {
  background: var(--letter-bg);
  color: var(--text);
}

.btn.secondary:hover {
  background: var(--letter-hover);
}

.btn.ghost {
  background: transparent;
  color: var(--muted);
  border: 1px solid #334155;
}

.btn.ghost:hover {
  color: var(--text);
  border-color: var(--muted);
}

/* Feedback */
.feedback {
  text-align: center;
  min-height: 28px;
  font-weight: 600;
  font-size: 1.1rem;
}

.feedback.success {
  color: var(--success);
}

.feedback.error {
  color: var(--error);
}

.feedback.hint {
  color: var(--warning);
}

/* Result */
.result h2 {
  font-size: 1.8rem;
  margin-bottom: 0.5rem;
}

.result-stats {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  margin: 1.5rem 0;
  font-size: 1.1rem;
}

.result-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Footer */
.footer {
  margin-top: auto;
  padding-top: 2rem;
  text-align: center;
  color: var(--muted);
  font-size: 0.8rem;
}

.footer code {
  background: #1e293b;
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.75rem;
}

/* Responsive */
@media (max-width: 480px) {
  .letter {
    width: 44px;
    height: 44px;
    font-size: 1.3rem;
  }
  .slot {
    width: 40px;
    height: 46px;
    font-size: 1.2rem;
  }
  .logo {
    font-size: 1.25rem;
  }
  .actions {
    flex-direction: column;
  }
  .btn {
    width: 100%;
  }
}

/* Version badge */
.version {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--muted);
  margin-left: 0.4rem;
  vertical-align: middle;
  background: #1e293b;
  padding: 0.15rem 0.4rem;
  border-radius: 6px;
  -webkit-text-fill-color: var(--muted);
}

.result-extra {
  color: var(--muted);
  font-size: 0.9rem;
  margin-top: 0.5rem;
}