body {
    margin: 0;
    padding: 0;
    height: 100vh;
    display: flex;
    flex-direction: column;      /* 縦に並べる */
    justify-content: center;
    align-items: center;
    background-color: #f5f5f5;
    font-family: sans-serif;
}

.main-container {
    background: #fff;
    padding: 20px 30px;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
    width: 320px;
}

.main-container form div {
    margin-bottom: 15px;
}

label {
    font-weight: bold;
    display: block;
    margin-bottom: 5px;
}

input[type="text"],
input[type="email"],
input[type="password"] {
    width: 100%;
    padding: 8px;
    border: 1px solid #ccc;
    border-radius: 5px;
    box-sizing: border-box;
}

input[type="submit"] {
    width: 100%;
    padding: 10px;
    background: #4CAF50;
    border: none;
    border-radius: 6px;
    color: white;
    font-size: 16px;
    cursor: pointer;
    transition: background 0.3s;
}

input[type="submit"]:hover {
    background: #45a049;
}

p {
    margin-top: 20px;
}

p a {
    color: #2196F3;
    text-decoration: none;
    font-weight: bold;
}

p a:hover {
    text-decoration: underline;
}