:root {
    --primary-color: #4a90e2;
    --primary-hover: #357abd;
    --bg-color: #f0f2f5;
    --text-color: #333;
    --card-bg: #fff;
    --error-color: #e74c3c;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.login-container {
    background-color: var(--card-bg);
    padding: 30px 40px;
    border-radius: 8px;
    box-shadow: var(--shadow);
    width: 320px;
    text-align: center;
}

.login-title {
    margin-bottom: 24px;
    font-weight: 500;
    color: #555;
}

.form-group {
    margin-bottom: 20px;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-size: 0.9em;
    color: #666;
}

.form-control {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    box-sizing: border-box; /* 重要: paddingを含めてwidthを計算 */
    font-size: 1em;
}

.form-control:focus {
    border-color: var(--primary-color);
    outline: none;
}

.form-options {
    display: flex;
    align-items: center;
    margin-bottom: 24px;
    font-size: 0.9em;
}

.form-options input[type="checkbox"] {
    margin-right: 8px;
}

.btn-login {
    width: 100%;
    padding: 12px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 1em;
    cursor: pointer;
    transition: background-color 0.2s;
}

.btn-login:hover {
    background-color: var(--primary-hover);
}

.error-message {
    color: var(--error-color);
    font-size: 0.9em;
    margin-bottom: 16px;
    background-color: #fceceb;
    padding: 10px;
    border-radius: 4px;
    border: 1px solid #f5c6cb;
}