.tool {
  max-width: 480px;
  margin: 30px auto;
  font-family: "Segoe UI",sans-serif;
  background: #fff;
  border: 1px solid rgba(0,0,0,0.1);
  border-radius: 20px;
  padding: 32px;
  box-shadow: 0 8px 32px rgba(0,0,0,0.08);
  transition: transform .3s, box-shadow .3s;
}

.tool:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 48px rgba(0,0,0,0.12);
}

.tool h2 {
  text-align: center;
  margin-bottom: 24px;
  color: var(--primary);
  font-size: 2rem;
  letter-spacing: 1px;
}

.tool label {
  display: block;
  margin-bottom: 16px;
  font-weight: 600;
  color: #222;
}

.tool input[type="number"] {
  width: 100%;
  padding: 10px;
  margin-top: 6px;
  box-sizing: border-box;
  border: 1px solid rgba(0,0,0,0.2);
  border-radius: 12px;
  transition: border-color .3s;
}

.tool input[type="number"]:focus {
  border-color: var(--accent);
  outline: none;
}

.tool button {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  border: none;
  padding: 12px;
  margin-top: 16px;
  cursor: pointer;
  border-radius: 16px;
  font-size: 1rem;
  transition: transform .3s, box-shadow .3s;
  width: 100%;
}

.tool button:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.15);
  background: linear-gradient(135deg, var(--secondary), var(--primary));
}

.tab-buttons {
  display: flex;
  justify-content: center;
  margin-bottom: 24px;
  gap: 8px;
}

.tab-buttons button {
  flex: 1;
  border-radius: 12px;
  background-color: #f0f0f0;
  color: #222;
  font-weight: 600;
  padding: 10px;
  transition: background .3s, color .3s;
}

.tab-buttons button.active {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
}

.tab-content {
  display: none;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity .5s, transform .5s;
}

.tab-content.active {
  display: block;
  opacity: 1;
  transform: translateY(0);
}

.result {
  margin-top: 20px;
  font-weight: 700;
  color: var(--dark);
  font-size: 1.1rem;
}

.formula {
  margin-top: 8px;
  color: #555;
  font-size: 14px;
  font-family: "Courier New", monospace;
}

/* body {
  margin: 0;
  padding: 0;
}
main, p, h2 { */
  /* margin-left: 20px;  ← 好きな余白に調整 */
  /* margin-right: 20px;
} */


.content {
  max-width: 480px;   /* ページ全体の横幅 */
  margin: 30px auto;    
  /* padding: 0 16px;    左右に余白 */
}