/* ========================================
   RechenStar Web — Styles
   Farben orientiert an der iOS-App
   ======================================== */

:root {
  /* Hauptfarben */
  --sky-blue: #4A90E2;
  --sun-yellow: #F5D547;
  --grass-green: #7ED321;
  --coral: #FF6B6B;
  --purple: #9B59B6;
  --orange: #FFA500;

  /* Hintergrund & Text */
  --bg: #F7F9FC;
  --card-bg: #FFFFFF;
  --text-primary: #2C3E50;
  --text-secondary: #7F8C8D;

  /* Schatten */
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);

  /* Rundungen */
  --radius: 16px;
  --radius-lg: 24px;
  --radius-round: 50%;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

html, body {
  height: 100%;
  overflow: hidden;
}

body {
  font-family: -apple-system, 'SF Pro Rounded', 'Nunito', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  user-select: none;
  -webkit-user-select: none;
}

#app {
  height: 100%;
  display: flex;
  flex-direction: column;
  width: 100%;
  max-width: 600px;
  margin: 0 auto;
}

/* ========================================
   Screens
   ======================================== */

.screen {
  display: none;
  flex-direction: column;
  height: 100%;
  padding: 16px;
  overflow-y: auto;
}

.screen.active {
  display: flex;
}

/* Exercise-Screen: festes Layout ohne Grössenänderung */
#screen-exercise {
  overflow: hidden;
  justify-content: space-between;
}

/* ========================================
   Home Screen
   ======================================== */

.home-header {
  text-align: center;
  padding: 24px 0 16px;
}

.home-back {
  display: inline-block;
  font-size: 14px;
  color: #8899aa;
  text-decoration: none;
  margin-bottom: 8px;
}

.home-back:hover {
  color: var(--sky-blue);
}

.home-title {
  font-size: 40px;
  font-weight: 800;
  color: var(--sky-blue);
  letter-spacing: -1px;
}

.home-greeting {
  font-size: 20px;
  color: var(--text-secondary);
  margin-top: 4px;
}

.home-stars {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 12px;
  font-size: 24px;
  font-weight: 700;
  color: var(--sun-yellow);
}

.home-stars .star-icon {
  font-size: 28px;
}

/* Streak-Anzeige */
.home-streak {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  margin-top: 8px;
  font-size: 16px;
  font-weight: 600;
  color: var(--orange);
}

/* Kategorien */
.category-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  padding: 8px 0;
  flex: 1;
  align-content: start;
}

.category-group-label {
  grid-column: 1 / -1;
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-secondary);
  padding: 8px 4px 0;
}

.category-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px 12px;
  text-align: center;
  box-shadow: var(--shadow);
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  border: 3px solid transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}

.category-card:active {
  transform: scale(0.95);
}

.category-card.selected {
  border-color: var(--sky-blue);
  box-shadow: var(--shadow-lg);
}

.category-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-round);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 26px;
  font-weight: 700;
  color: white;
}

.category-icon.addition { background: var(--sky-blue); }
.category-icon.subtraction { background: var(--coral); }
.category-icon.multiplication { background: var(--purple); }

.category-name {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
}

.category-detail {
  font-size: 12px;
  color: var(--text-secondary);
}

/* Start-Button */
.start-section {
  padding: 12px 0 24px;
}

.btn-start {
  width: 100%;
  padding: 18px;
  font-size: 22px;
  font-weight: 700;
  color: white;
  background: var(--sky-blue);
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, background 0.15s ease;
}

.btn-start:active {
  transform: scale(0.97);
  background: #3a7bc8;
}

.btn-start:disabled {
  background: #B0C4DE;
  cursor: not-allowed;
}

/* ========================================
   Exercise Screen
   ======================================== */

.exercise-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 0;
}

.exercise-progress-text {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-secondary);
}

.exercise-stars {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 18px;
  font-weight: 700;
  color: var(--sun-yellow);
}

.btn-close {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-round);
  border: none;
  background: #EEF2F7;
  font-size: 18px;
  font-weight: 700;
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Fortschrittsbalken */
.progress-bar-container {
  height: 8px;
  background: #EEF2F7;
  border-radius: 4px;
  margin: 4px 0 12px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: var(--sky-blue);
  border-radius: 4px;
  transition: width 0.4s ease;
}

/* Aufgaben-Karte */
.exercise-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: 24px 16px;
  text-align: center;
  flex: 1 0 auto;
  min-height: 160px;
  max-height: 240px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.exercise-display {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
  min-height: 72px;
}

.exercise-number {
  font-size: 52px;
  font-weight: 700;
  color: var(--text-primary);
  min-width: 40px;
}

.exercise-operator {
  font-size: 40px;
  font-weight: 700;
  color: var(--sky-blue);
}

.exercise-equals {
  font-size: 40px;
  font-weight: 700;
  color: var(--text-secondary);
}

.exercise-gap {
  font-size: 52px;
  font-weight: 700;
  color: var(--sky-blue);
  min-width: 56px;
  border-bottom: 4px solid var(--sky-blue);
  padding: 0 4px;
}

/* Antwort-Anzeige */
.answer-display {
  margin-top: 12px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.answer-value {
  font-size: 48px;
  font-weight: 700;
  color: var(--sky-blue);
  min-width: 60px;
  text-align: center;
  border-bottom: 4px solid var(--sky-blue);
  padding: 0 8px;
  transition: color 0.2s;
}

.answer-value.correct {
  color: var(--grass-green);
  border-color: var(--grass-green);
}

.answer-value.incorrect {
  color: var(--coral);
  border-color: var(--coral);
}

.answer-value.empty::after {
  content: '_';
  opacity: 0.3;
}

/* Shake-Animation */
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-12px); }
  40% { transform: translateX(12px); }
  60% { transform: translateX(-8px); }
  80% { transform: translateX(8px); }
}

.shake {
  animation: shake 0.4s ease-in-out;
}

/* Feedback-Bereich */
.feedback-area {
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.feedback-text {
  font-size: 18px;
  font-weight: 700;
  text-align: center;
  opacity: 0;
  transition: opacity 0.3s;
}

.feedback-text.visible {
  opacity: 1;
}

.feedback-text.correct {
  color: var(--grass-green);
}

.feedback-text.incorrect {
  color: var(--coral);
}

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

.feedback-text.answer {
  color: var(--grass-green);
}

/* Sterne-Feedback */
.feedback-stars {
  display: flex;
  gap: 8px;
  font-size: 32px;
}

@keyframes star-pop {
  0% { transform: scale(0); opacity: 0; }
  50% { transform: scale(1.3); }
  100% { transform: scale(1); opacity: 1; }
}

.feedback-stars span {
  animation: star-pop 0.4s ease forwards;
  opacity: 0;
}

.feedback-stars span:nth-child(2) {
  animation-delay: 0.15s;
}

/* Nummernpad */
.numpad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
  padding: 8px 16px;
  max-width: 340px;
  margin: 0 auto;
  width: 100%;
}

.numpad-btn {
  aspect-ratio: 1;
  border-radius: var(--radius-round);
  border: none;
  font-size: 28px;
  font-weight: 700;
  color: var(--text-primary);
  background: var(--card-bg);
  box-shadow: var(--shadow);
  cursor: pointer;
  transition: transform 0.1s ease, background 0.1s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  max-width: 80px;
  max-height: 80px;
  width: 100%;
  justify-self: center;
}

.numpad-btn:active {
  transform: scale(0.9);
  background: #EEF2F7;
}

.numpad-btn.delete {
  background: #EEF2F7;
  color: var(--text-secondary);
  font-size: 22px;
}

.numpad-btn.submit {
  background: var(--grass-green);
  color: white;
  font-size: 26px;
}

.numpad-btn.submit:active {
  background: #6bc318;
}

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

/* Überspringen */
.skip-section {
  text-align: center;
  height: 40px;
  flex-shrink: 0;
}

.btn-skip {
  background: none;
  border: none;
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  padding: 8px 16px;
}

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

/* ========================================
   Results Screen
   ======================================== */

.results-screen {
  align-items: center;
  justify-content: center;
  gap: 20px;
  padding: 24px 16px;
}

.results-title {
  font-size: 36px;
  font-weight: 800;
  color: var(--sky-blue);
}

.results-stars-display {
  display: flex;
  gap: 8px;
  font-size: 44px;
}

@keyframes result-star {
  0% { transform: scale(0) rotate(-30deg); opacity: 0; }
  60% { transform: scale(1.2) rotate(10deg); }
  100% { transform: scale(1) rotate(0deg); opacity: 1; }
}

.results-stars-display span {
  opacity: 0;
  animation: result-star 0.5s ease forwards;
}

.results-stars-display span:nth-child(2) { animation-delay: 0.15s; }
.results-stars-display span:nth-child(3) { animation-delay: 0.3s; }
.results-stars-display span:nth-child(4) { animation-delay: 0.45s; }
.results-stars-display span:nth-child(5) { animation-delay: 0.6s; }

.results-star-text {
  font-size: 22px;
  font-weight: 700;
  color: var(--sun-yellow);
}

/* Stats-Karten */
.results-stats {
  display: flex;
  gap: 12px;
  width: 100%;
}

.stat-card {
  flex: 1;
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px 8px;
  text-align: center;
  box-shadow: var(--shadow);
}

.stat-icon {
  font-size: 24px;
  margin-bottom: 4px;
}

.stat-value {
  font-size: 22px;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}

/* Level-Anzeige */
.results-level {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px 24px;
  box-shadow: var(--shadow);
  text-align: center;
  width: 100%;
}

.results-level-title {
  font-size: 14px;
  color: var(--text-secondary);
  font-weight: 600;
}

.results-level-name {
  font-size: 20px;
  font-weight: 700;
  color: var(--purple);
  margin: 4px 0;
}

.results-level-progress {
  height: 8px;
  background: #EEF2F7;
  border-radius: 4px;
  overflow: hidden;
  margin-top: 8px;
}

.results-level-progress-fill {
  height: 100%;
  background: var(--purple);
  border-radius: 4px;
  transition: width 1s ease;
}

.results-level-next {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* Streak */
.results-streak {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
  color: var(--orange);
}

/* Home-Button */
.btn-home {
  width: 100%;
  padding: 16px;
  font-size: 20px;
  font-weight: 700;
  color: white;
  background: var(--sky-blue);
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  box-shadow: var(--shadow);
  margin-top: 8px;
}

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

/* ========================================
   Confetti
   ======================================== */

.confetti-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 100;
  overflow: hidden;
}

@keyframes confetti-fall {
  0% { transform: translateY(-10px) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

.confetti-piece {
  position: absolute;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  animation: confetti-fall linear forwards;
}

/* ========================================
   Responsive
   ======================================== */

/* Kleine Bildschirme / Tablets im Querformat */
@media (max-height: 600px) {
  .exercise-number { font-size: 36px; }
  .exercise-operator, .exercise-equals { font-size: 28px; }
  .exercise-gap { font-size: 36px; }
  .answer-value { font-size: 36px; }
  .exercise-card { padding: 12px; }
  .numpad { gap: 6px; padding: 4px 16px; }
  .numpad-btn { font-size: 22px; max-width: 60px; max-height: 60px; }
  .feedback-area { height: 36px; }
  .exercise-card { max-height: 160px; min-height: 120px; }
  .home-header { padding: 12px 0 8px; }
  .home-title { font-size: 30px; }
}

/* Tablets und grösser */
@media (min-width: 600px) {
  #app { max-width: 600px; }
  .screen { padding: 24px 32px; }
  .category-grid { gap: 16px; }
  .category-card { padding: 20px 16px; }
  .category-icon { width: 56px; height: 56px; font-size: 30px; }
  .category-name { font-size: 16px; }
  .numpad { max-width: 380px; gap: 12px; }
  .numpad-btn { max-width: 88px; max-height: 88px; font-size: 32px; }
  .btn-start { font-size: 24px; padding: 20px; }
  .exercise-number { font-size: 64px; }
  .exercise-operator, .exercise-equals { font-size: 48px; }
  .exercise-gap { font-size: 64px; }
  .answer-value { font-size: 56px; }
  .exercise-card { min-height: 180px; max-height: 280px; padding: 28px 20px; }
  .home-title { font-size: 48px; }
  .feedback-area { height: 52px; }
  .feedback-text { font-size: 20px; }
  .feedback-stars { font-size: 36px; }
}