:root {
  --bg: #0f1620;
  --panel: #1a2533;
  --panel-light: #233044;
  --accent: #4fd1c5;
  --accent-dark: #2ca39a;
  --text: #eef3f8;
  --text-dim: #9fb0c2;
  --correct: #4ade80;
  --incorrect: #f87171;

  --diff-1: #4ade80;
  --diff-2: #facc15;
  --diff-3: #fb923c;
  --diff-4: #f87171;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
}

#app {
  max-width: 1000px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
}

.screen { display: none; }
.screen.active { display: block; }

h1 {
  text-align: center;
  font-size: 2.2rem;
  margin-bottom: 4px;
  letter-spacing: 1px;
}

.subtitle {
  text-align: center;
  color: var(--text-dim);
  margin-top: 0;
  margin-bottom: 28px;
}

.setup-group {
  margin-bottom: 24px;
}

.setup-group h2 {
  font-size: 1.05rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 1.5px;
  margin-bottom: 10px;
  font-weight: 600;
}

.setup-group h2 .hint {
  text-transform: none;
  letter-spacing: normal;
  font-weight: 400;
  font-size: 0.85rem;
  opacity: 0.8;
}

.options-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

.option-btn {
  background: var(--panel);
  border: 2px solid transparent;
  border-radius: 10px;
  padding: 14px 16px;
  text-align: left;
  cursor: pointer;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 4px;
  transition: border-color 0.15s, background 0.15s, transform 0.1s;
}

.option-btn:hover {
  background: var(--panel-light);
  transform: translateY(-1px);
}

.option-btn.selected {
  border-color: var(--accent);
  background: var(--panel-light);
}

#difficulty-options .option-btn[data-difficulty="1"] { border-color: color-mix(in srgb, var(--diff-1) 35%, transparent); }
#difficulty-options .option-btn[data-difficulty="2"] { border-color: color-mix(in srgb, var(--diff-2) 35%, transparent); }
#difficulty-options .option-btn[data-difficulty="3"] { border-color: color-mix(in srgb, var(--diff-3) 35%, transparent); }
#difficulty-options .option-btn[data-difficulty="4"] { border-color: color-mix(in srgb, var(--diff-4) 35%, transparent); }

#difficulty-options .option-btn[data-difficulty="1"].selected { border-color: var(--diff-1); box-shadow: 0 0 0 1px var(--diff-1) inset; }
#difficulty-options .option-btn[data-difficulty="2"].selected { border-color: var(--diff-2); box-shadow: 0 0 0 1px var(--diff-2) inset; }
#difficulty-options .option-btn[data-difficulty="3"].selected { border-color: var(--diff-3); box-shadow: 0 0 0 1px var(--diff-3) inset; }
#difficulty-options .option-btn[data-difficulty="4"].selected { border-color: var(--diff-4); box-shadow: 0 0 0 1px var(--diff-4) inset; }

/* ---------- Toggle checkbox ---------- */

#extras-group .toggle-label + .toggle-label {
  margin-top: 10px;
}

.toggle-label {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  background: var(--panel);
  border: 2px solid transparent;
  border-radius: 10px;
  padding: 14px 16px;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.toggle-label:hover {
  background: var(--panel-light);
}

.toggle-label:has(input:checked) {
  border-color: var(--accent);
  background: var(--panel-light);
}

.toggle-label input[type="checkbox"] {
  width: 20px;
  height: 20px;
  accent-color: var(--accent);
  cursor: pointer;
  flex-shrink: 0;
}

.toggle-text {
  font-weight: 700;
  font-size: 1.05rem;
}

.toggle-label .opt-desc {
  width: 100%;
  margin-left: 30px;
}

.opt-title {
  font-weight: 700;
  font-size: 1.05rem;
}

.opt-desc {
  font-size: 0.82rem;
  color: var(--text-dim);
}

.primary-btn {
  display: block;
  width: 100%;
  margin-top: 8px;
  padding: 14px;
  font-size: 1.1rem;
  font-weight: 700;
  border: none;
  border-radius: 10px;
  background: var(--accent);
  color: #06231f;
  cursor: pointer;
  transition: background 0.15s, opacity 0.15s;
}

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

.primary-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.back-link { text-align: center; margin-top: 16px; font-size: 0.9rem; }
.back-link a { color: var(--muted); text-decoration: none; }
.back-link a:hover { color: var(--accent); }

.how-to {
  border: 1px solid var(--panel-light);
  border-radius: 8px;
  margin-top: 20px;
  background: var(--panel);
  max-width: 520px;
  width: 100%;
  text-align: left;
}

.how-to-summary {
  display: block;
  padding: 10px 14px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 1px;
  cursor: pointer;
  list-style: none;
  user-select: none;
}
.how-to-summary::-webkit-details-marker { display: none; }
.how-to-summary::before {
  content: "\25B8";
  display: inline-block;
  margin-right: 8px;
  transition: transform 0.2s;
}
details.how-to[open] > .how-to-summary::before { transform: rotate(90deg); }
.how-to-summary:hover { color: var(--text); }

.how-to-body { padding: 0 16px 12px; }
.how-to-body p {
  font-size: 0.9rem;
  color: var(--text-dim);
  line-height: 1.55;
  margin: 0 0 10px;
}
.how-to-body p:last-child { margin-bottom: 0; }
.how-to-body strong { color: var(--text); }

.text-btn {
  background: none;
  border: none;
  color: var(--text-dim);
  cursor: pointer;
  font-size: 0.95rem;
  text-decoration: underline;
}

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

/* ---------- Game screen ---------- */

.game-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.hud {
  display: flex;
  gap: 18px;
  font-weight: 600;
  color: var(--text-dim);
}

#score-counter { color: var(--accent); }

.flag-wrap {
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--panel);
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid #233044;
  padding: 32px;
  min-height: 280px;
}

.flag-container {
  position: relative;
  display: inline-block;
  max-width: 400px;
  width: 100%;
  border-radius: 6px;
  overflow: hidden;
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.5);
}

#flag-img {
  display: block;
  width: 100%;
  height: auto;
}

.quadrant-overlay {
  position: absolute;
  width: 50%;
  height: 50%;
  background: var(--panel);
  transition: opacity 0.4s;
  pointer-events: none;
}

.quadrant-overlay[data-q="0"] { top: 0;   left: 0;  }
.quadrant-overlay[data-q="1"] { top: 0;   left: 50%; }
.quadrant-overlay[data-q="2"] { top: 50%; left: 0;  }
.quadrant-overlay[data-q="3"] { top: 50%; left: 50%; }

.quadrant-overlay.revealed {
  opacity: 0;
}

.quadrant-overlay.no-transition {
  transition: none;
}

.quadrant-overlay.hidden-mode {
  display: none;
}

/* ---------- Flash mode ---------- */

.flash-overlay {
  position: absolute;
  inset: 0;
  background: var(--panel);
  opacity: 0;
  pointer-events: none;
  transition: none;
}

.flash-overlay.hidden {
  opacity: 1;
}

.flash-overlay.fade-out {
  transition: opacity 0.3s ease-out;
  opacity: 0;
}

.flash-overlay.hidden-mode {
  display: none;
}

.feedback-banner {
  text-align: center;
  padding: 10px 22px;
  border-radius: 8px;
  font-weight: 700;
  font-size: 1.1rem;
  margin-top: 12px;
}

.feedback-banner.correct {
  background: var(--correct);
  color: #06270f;
}

.feedback-banner.incorrect {
  background: var(--incorrect);
  color: #2a0606;
}

.feedback-banner.hidden { display: none; }

.answer-area {
  margin-top: 18px;
}

#question-text {
  text-align: center;
  font-size: 1.2rem;
  margin-bottom: 14px;
}

.answers {
  grid-template-columns: repeat(3, 1fr);
}

.answer-btn {
  background: var(--panel);
  border: 2px solid transparent;
  border-radius: 10px;
  padding: 16px;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.answer-btn:hover:not(:disabled) {
  background: var(--panel-light);
  border-color: var(--accent);
}

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

.answer-btn.correct {
  background: rgba(74, 222, 128, 0.18);
  border-color: var(--correct);
}

.answer-btn.incorrect {
  background: rgba(248, 113, 113, 0.18);
  border-color: var(--incorrect);
}

.answer-form {
  display: flex;
  gap: 10px;
}

.answer-form.hidden { display: none; }

#answer-input {
  flex: 1;
  padding: 14px 16px;
  font-size: 1.05rem;
  border-radius: 10px;
  border: 2px solid var(--panel-light);
  background: var(--panel);
  color: var(--text);
  transition: border-color 0.2s, background 0.2s;
}

#answer-input:focus {
  outline: none;
  box-shadow: 0 0 0 2px var(--accent);
}

#answer-input.correct {
  background: rgba(74, 222, 128, 0.16);
}

#answer-input.incorrect {
  background: rgba(248, 113, 113, 0.16);
}

#answer-form #submit-btn {
  width: auto;
  margin-top: 0;
  padding: 14px 24px;
  flex-shrink: 0;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.options-grid.answers.hidden { display: none; }

/* ---------- Attempt pips (reveal mode) ---------- */

.attempt-pips {
  display: flex;
  gap: 8px;
  justify-content: center;
  margin-bottom: 12px;
}

.attempt-pips.hidden { display: none; }

.pip {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 2px solid var(--text-dim);
  background: transparent;
  transition: background 0.2s, border-color 0.2s;
}

.pip.used {
  background: var(--incorrect);
  border-color: var(--incorrect);
}

.pip.correct {
  background: var(--correct);
  border-color: var(--correct);
}


.final-score {
  text-align: center;
  font-size: 1.4rem;
  color: var(--accent);
  font-weight: 700;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%       { transform: translateX(-6px); }
  40%       { transform: translateX(6px); }
  60%       { transform: translateX(-4px); }
  80%       { transform: translateX(4px); }
}

.shake { animation: shake 0.35s ease; }

@media (max-width: 600px) {
  .options-grid { grid-template-columns: 1fr; }
  .answers { grid-template-columns: repeat(2, 1fr); }
  h1 { font-size: 1.6rem; }
  #flag-img { max-width: 280px; }
  .flag-wrap { padding: 20px; min-height: 200px; }
}

/* Chain Memory mode */
.answers.chain-recall {
  grid-template-columns: repeat(3, 1fr);
}

.answer-btn.selected {
  border-color: var(--accent);
  background: rgba(79, 209, 197, 0.12);
}

.answer-btn.missed {
  border-color: var(--correct);
  background: rgba(74, 222, 128, 0.08);
  opacity: 0.6;
}

.chain-slots {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
  margin-bottom: 16px;
}

.chain-slot {
  background: var(--panel-light);
  border: 2px solid transparent;
  border-radius: 8px;
  padding: 8px 16px;
  font-size: 0.95rem;
  font-weight: 600;
  min-width: 130px;
  text-align: center;
  color: var(--text-dim);
}

.chain-slot.correct {
  border-color: var(--correct);
  color: var(--correct);
  background: rgba(74, 222, 128, 0.08);
}

.chain-slot.incorrect {
  border-color: var(--incorrect);
  color: var(--incorrect);
  background: rgba(248, 113, 113, 0.08);
}

/* Duels mode */
body.duels-mode #difficulty-setup-group { display: none; }

.option-btn-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: auto;
  padding: 10px 20px;
  font-weight: 700;
}

.player-name-input {
  background: var(--panel-light);
  border: 2px solid var(--panel-light);
  border-radius: 8px;
  color: var(--text);
  font-size: 1rem;
  padding: 12px 16px;
  text-align: center;
  outline: none;
  width: 100%;
}
.player-name-input:focus { border-color: var(--accent); }
.player-name-input::placeholder { color: var(--text-dim); }

.duel-hud {
  display: flex;
  align-items: center;
  gap: 12px;
}
.duel-player-chip {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 6px 14px;
  border-radius: 8px;
  background: var(--panel-light);
  opacity: 0.5;
  transition: opacity 0.2s, background 0.2s;
  min-width: 80px;
}
.duel-player-chip.active {
  background: var(--accent);
  opacity: 1;
  color: #000;
}
.duel-player-name { font-size: 0.75rem; font-weight: 600; white-space: nowrap; overflow: hidden; max-width: 100px; text-overflow: ellipsis; }
.duel-player-score { font-size: 1.4rem; font-weight: 700; line-height: 1.2; }
.duel-vs { font-size: 0.85rem; color: var(--text-dim); font-weight: 600; }

.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 200;
}
.modal-overlay.hidden { display: none !important; }
.modal-box {
  background: var(--panel);
  border-radius: 16px;
  padding: 2rem;
  max-width: 400px;
  width: 90%;
  text-align: center;
}
.modal-box h2 { margin-top: 0; }
.modal-box ul { text-align: left; line-height: 2; padding-left: 1.2rem; }