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

body {
  background-color: #eaf6ff;
  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 Biru Toska Air */
.header {
  background: linear-gradient(135deg, #00cec9, #0984e3);
  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: #e1f5fe;
  border-bottom: 2px solid #b3e5fc;
}

.nav-btn {
  flex: 1;
  padding: 12px 2px;
  border: none;
  background: none;
  font-size: 0.88rem;
  font-weight: bold;
  color: #546e7a;
  cursor: pointer;
  transition: 0.3s;
}

.nav-btn.active {
  background-color: #ffffff;
  color: #0984e3;
  border-bottom: 3px solid #0984e3;
}

.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: #0984e3;
  margin-bottom: 10px;
}

.rule-box {
  background-color: #e1f5fe;
  border-left: 4px solid #0984e3;
  padding: 10px 12px;
  border-radius: 6px;
  line-height: 1.6;
}

/* Visual Tangga Satuan */
.stair-container {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin: 10px 0;
}

.stair-step {
  padding: 8px 12px;
  background-color: #f0f4f8;
  border-left: 5px solid #00cec9;
  border-radius: 6px;
  font-size: 0.9rem;
  transition: all 0.2s ease;
}

.stair-step:nth-child(1) { margin-left: 0px; }
.stair-step:nth-child(2) { margin-left: 15px; }
.stair-step:nth-child(3) { margin-left: 30px; }
.stair-step:nth-child(4) { margin-left: 45px; background-color: #e3f2fd; border-left-color: #0984e3; }
.stair-step:nth-child(5) { margin-left: 60px; }
.stair-step:nth-child(6) { margin-left: 75px; }
.stair-step:nth-child(7) { margin-left: 90px; }

.stair-step.active-step {
  background-color: #ffeaa7;
  border-left-color: #fdcb6e;
  font-weight: bold;
}

.example-box {
  background-color: #f7f9fa;
  border: 1px dashed #0984e3;
  padding: 10px;
  border-radius: 6px;
  font-size: 0.9rem;
  line-height: 1.6;
}

/* Form Kalkulator */
.input-group {
  margin: 10px 0;
  flex: 1;
}

.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;
}

.select-row {
  display: flex;
  align-items: center;
  gap: 10px;
}

.arrow-icon {
  font-size: 1.2rem;
  margin-top: 15px;
}

.result-box {
  background-color: #e1f5fe;
  border-left: 4px solid #0984e3;
  padding: 12px;
  border-radius: 6px;
  margin-top: 15px;
  text-align: center;
}

#resultText {
  font-size: 1.2rem;
  font-weight: bold;
  color: #0984e3;
  margin-bottom: 5px;
}

.step-text {
  font-size: 0.88rem;
  color: #546e7a;
}

/* 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 #0984e3;
  background-color: #fff;
  color: #0984e3;
  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: #0984e3;
  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;
}