:root {
  --bg-color: #f2f2f7; /* iOS background gray */
  --app-bg: #ffffff;
  --text-color: #000000;
  --text-secondary: #8e8e93;
  --blue-primary: #007aff;
  --blue-active: #0056b3;
  --border-color: #c6c6c8;
  --input-bg: #f2f2f7;
}

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

body {
  font-family: 'Noto Sans JP', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  display: flex;
  justify-content: center;
  align-items: flex-start;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.app-container {
  width: 100%;
  max-width: 375px;
  min-height: 100vh;
  background-color: var(--app-bg);
  box-shadow: 0 0 20px rgba(0,0,0,0.05);
  display: flex;
  flex-direction: column;
}

.app-header {
  padding: 16px;
  text-align: center;
  border-bottom: 0.5px solid var(--border-color);
  background-color: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.app-header h1 {
  font-size: 17px;
  font-weight: 600;
}

.app-content {
  padding: 24px 16px;
  flex: 1;
}

.input-group {
  margin-bottom: 20px;
}

.input-group label {
  display: block;
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 8px;
  font-weight: 500;
}

.input-group input {
  width: 100%;
  height: 50px;
  border: none;
  background-color: var(--input-bg);
  border-radius: 10px;
  padding: 0 16px;
  font-size: 16px;
  font-family: inherit;
  outline: none;
  transition: background-color 0.2s;
}

.input-group input:focus {
  background-color: #e5e5ea;
}

.calc-btn {
  width: 100%;
  height: 56px;
  background-color: var(--blue-primary);
  color: white;
  border: none;
  border-radius: 14px;
  font-size: 17px;
  font-weight: 600;
  margin-top: 12px;
  margin-bottom: 32px;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  transition: background-color 0.2s, transform 0.1s;
}

.calc-btn:active {
  background-color: var(--blue-active);
  transform: scale(0.98);
}

.result-section {
  background-color: var(--app-bg);
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
}

.result-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 0;
}

.result-label {
  font-size: 16px;
  font-weight: 500;
}

.result-value {
  font-size: 20px;
  font-weight: 700;
}

.result-divider {
  height: 1px;
  background-color: var(--border-color);
  margin: 8px 0;
}

.highlight .result-label,
.highlight .result-value {
  color: var(--blue-primary);
}

.highlight .result-value {
  font-size: 22px;
}