* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
  background-color: #f3f0f7;
  color: #2c3e50;
  display: flex;
  justify-content: center;
}

.app-container {
  width: 100%;
  max-width: 480px;
  min-height: 100vh;
  background-color: #ffffff;
  box-shadow: 0 0 15px rgba(0,0,0,0.08);
  display: flex;
  flex-direction: column;
}

/* Header Tema Pink/Merah Muda Ceria */
.header {
  background: linear-gradient(135deg, #e84393, #fd79a8);
  color: white;
  text-align: center;
  padding: 20px 15px;
}

.header h1 {
  font-size: 1.4rem;
  margin-bottom: 5px;
}

.header p {
  font-size: 0.88rem;
  opacity: 0.95;
}

.nav-menu {
  display: flex;
  background-color: #fce4ec;
  border-bottom: 2px solid #f8bbd0;
}

.nav-btn {
  flex: 1;
  padding: 12px 2px;
  border: none;
  background: none;
  font-size: 0.88rem;
  font-weight: bold;
  color: #880e4f;
  cursor: pointer;
  transition: 0.3s;
}

.nav-btn.active {
  background-color: #ffffff;
  color: #e84393;
  border-bottom: 3px solid #e84393;
}

.content {
  padding: 15px;
  flex: 1;
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

.card {
  background-color: #ffffff;
  border-radius: 12px;
  padding: 15px;
  margin-bottom: 15px;
  border: 1px solid #e1e8f0;
  box-shadow: 0 2px 5px rgba(0,0,0,0.04);
}

.card h2 {
  font-size: 1.05rem;
  color: #e84393;
  margin-bottom: 10px;
}

/* Shape Selector Buttons */
.shape-selector {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.shape-btn {
  padding: 8px 12px;
  border: 1px solid #e84393;
  background-color: #fff;
  color: #e84393;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: bold;
  cursor: pointer;
  transition: 0.2s;
}

.shape-btn.active {
  background-color: #e84393;
  color: white;
}

/* Graphic Shape Preview Box */
.shape-preview-box {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 120px;
  background-color: #fce4ec;
  border-radius: 8px;
  margin: 10px 0;
}

.visual-shape {
  border: 3px solid #e84393;
  background-color: #fd79a8;
}

.visual-shape.persegi {
  width: 70px;
  height: 70px;
}

.visual-shape.persegiPanjang {
  width: 100px;
  height: 60px;
}

.visual-shape.segitiga {
  width: 0;
  height: 0;
  border-left: 45px solid transparent;
  border-right: 45px solid transparent;
  border-bottom: 75px solid #e84393;
  background-color: transparent;
  border-top: none;
}

.visual-shape.lingkaran {
  width: 75px;
  height: 75px;
  border-radius: 50%;
}

.visual-shape.jajarGenjang {
  width: 90px;
  height: 55px;
  transform: skew(-20deg);
}

.visual-shape.trapesium {
  width: 90px;
  height: 0;
  border-bottom: 50px solid #e84393;
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
  background-color: transparent;
  border-top: none;
}

.formula-box, .rule-box {
  background-color: #fce4ec;
  border-left: 4px solid #e84393;
  padding: 10px 12px;
  border-radius: 6px;
  margin: 10px 0;
  font-size: 0.9rem;
  line-height: 1.5;
}

.sub-card {
  background-color: #fff5f8;
  border: 1px solid #fd79a8;
  border-radius: 8px;
  padding: 12px;
  margin: 10px 0;
}

.input-group {
  margin: 10px 0;
}

.input-group label {
  display: block;
  margin-bottom: 5px;
  font-size: 0.85rem;
  font-weight: bold;
}

.input-group input, .input-group select {
  width: 100%;
  padding: 8px;
  border: 1px solid #b2bec3;
  border-radius: 6px;
  font-size: 0.95rem;
}

.result-box {
  background-color: #fce4ec;
  border-left: 4px solid #e84393;
  padding: 12px;
  border-radius: 6px;
  margin-top: 15px;
}

.result-box p {
  font-size: 1rem;
  font-weight: bold;
  color: #880e4f;
  margin: 4px 0;
}

/* Kuis Style */
.quiz-header {
  font-size: 0.85rem;
  color: #777;
  margin-bottom: 8px;
}

.question {
  font-weight: bold;
  font-size: 0.98rem;
  margin-bottom: 12px;
}

.options-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-btn {
  padding: 12px;
  border: 1px solid #e84393;
  background-color: #fff;
  color: #e84393;
  border-radius: 8px;
  font-size: 0.95rem;
  text-align: left;
  cursor: pointer;
  transition: 0.2s;
}

.option-btn.correct {
  background-color: #00b894;
  color: white;
  border-color: #00b894;
}

.option-btn.wrong {
  background-color: #ff7675;
  color: white;
  border-color: #ff7675;
}

.feedback {
  margin-top: 10px;
  font-weight: bold;
  text-align: center;
}

.action-btn {
  width: 100%;
  padding: 12px;
  margin-top: 15px;
  background-color: #e84393;
  color: white;
  border: none;
  border-radius: 8px;
  font-weight: bold;
  font-size: 0.98rem;
  cursor: pointer;
}

.score-box {
  text-align: center;
  font-size: 3rem;
  font-weight: bold;
  color: #00b894;
  margin: 15px 0;
}