body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f6f8;
    color: #333;
}

header {
    background-color: #1a73e8;
    color: white;
    padding: 20px;
    text-align: center;
}

main {
    max-width: 900px;
    margin: 40px auto;
    padding: 20px;
    background-color: white;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    border-radius: 8px;
}

h1, h2 {
    margin-top: 0;
}

.section {
    margin-bottom: 30px;
}

.button-link {
    display: inline-block;
    padding: 12px 20px;
    margin: 10px 10px 10px 0;
    background-color: #1a73e8;
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-weight: bold;
}

.button-link:hover {
    background-color: #1558b0;
}

.lang-bar {
    background-color: #1558b0;
    text-align: center;
    padding: 12px;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 6px rgba(0,0,0,0.25);
}

.lang-toggle-label {
    display: inline-flex;
    align-items: center;
    gap: 14px;
    color: white;
    font-size: 1.2em;
    font-weight: bold;
    cursor: pointer;
    user-select: none;
}

.lang-toggle-switch {
    position: relative;
    display: inline-block;
    width: 76px;
    height: 38px;
}

.lang-toggle-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.lang-slider {
    position: absolute;
    cursor: pointer;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: rgba(255, 255, 255, 0.35);
    border-radius: 38px;
    transition: background-color 0.3s;
}

.lang-slider::before {
    content: "";
    position: absolute;
    height: 30px;
    width: 30px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    border-radius: 50%;
    transition: transform 0.3s;
}

.lang-toggle-switch input:checked + .lang-slider {
    background-color: rgba(255, 255, 255, 0.55);
}

.lang-toggle-switch input:checked + .lang-slider::before {
    transform: translateX(38px);
}

.lang-ja {
    display: none;
}

.auth-section {
    background-color: #e8f4fd;
    border: 3px solid #1a73e8;
    border-radius: 10px;
    padding: 28px 32px;
    margin-bottom: 30px;
}

.auth-section h2 {
    color: #0d47a1;
    font-size: 1.7em;
}

.auth-section p,
.auth-section li {
    font-size: 1.2em;
    line-height: 1.9;
}

.button-auth {
    display: block;
    width: fit-content;
    margin: 24px auto 12px;
    padding: 22px 48px;
    background-color: #e53935;
    color: white;
    text-decoration: none;
    border-radius: 10px;
    font-size: 1.5em;
    font-weight: bold;
    text-align: center;
    letter-spacing: 0.03em;
}

.button-auth:hover {
    background-color: #b71c1c;
}

.auth-note {
    font-size: 1em;
    color: #555;
    text-align: center;
    margin-top: 8px;
}

footer {
    text-align: center;
    padding: 20px;
    font-size: 0.9em;
    color: #666;
}