body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 20px;
    background-color: #f4f4f9;
    color: #333;
}
.container {
    max-width: 500px;
    margin: 0 auto;
    background-color: #fff;
    padding: 25px;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
}
h2 {
    text-align: center;
    color: #17a2b8; /* ナイトロックスイメージのシアン/青緑系 */
    border-bottom: 2px solid #17a2b8;
    padding-bottom: 10px;
    margin-bottom: 20px;
}
h3 {
    color: #555;
    margin-top: 25px;
    margin-bottom: 15px;
}
.input-group {
    margin-bottom: 15px;
}
label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}
input[type="number"], select {
    width: calc(100% - 12px);
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    box-sizing: border-box;
    font-size: 1em;
}
.note {
    font-size: 0.85em;
    color: #666;
    margin-top: 4px;
}
.result-group {
    padding: 15px;
    border: 1px solid #ddd;
    border-radius: 5px;
    background-color: #e9ecef;
}
.result-group p {
    margin: 8px 0;
    font-size: 1.1em;
}
.result-group hr {
    border: 0;
    border-top: 1px dashed #ccc;
    margin: 15px 0;
}
.highlight-blue {
    font-size: 1.4em;
    font-weight: bold;
    color: #0056b3;
}
.warning {
    color: #dc3545;
    font-weight: bold;
    margin-top: 10px;
    padding: 10px;
    background-color: #f8d7da;
    border: 1px solid #f5c6cb;
    border-radius: 5px;
    text-align: center;
}
.hidden {
    display: none;
}
/* PO2値に応じた色変化用クラス */
.safe { color: #28a745; font-weight: bold; }
.caution { color: #ffc107; font-weight: bold; } /* 1.4超え */
.danger { color: #dc3545; font-weight: bold; }  /* 1.6超え */