body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: #f5f5f5;
    margin: 0;
    font-family: sans-serif;
}
.login-card {
    background: #fff;
    border-radius: 8px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.12);
    padding: 40px 48px;
    width: 100%;
    max-width: 400px;
}
.login-card h1 {
    font-size: 1.5rem;
    margin-bottom: 28px;
    text-align: center;
    color: #333;
}
.form-group {
    margin-bottom: 18px;
}
.form-group label {
    display: block;
    font-size: 0.875rem;
    color: #555;
    margin-bottom: 6px;
}
.form-group input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid #ccc;
    border-radius: 5px;
    font-size: 1rem;
    box-sizing: border-box;
    transition: border-color 0.2s;
}
.form-group input:focus {
    outline: none;
    border-color: #4f8ef7;
}
.form-group input.is-invalid {
    border-color: #e74c3c;
}
.invalid-feedback {
    color: #e74c3c;
    font-size: 0.8rem;
    margin-top: 4px;
}
.remember-row {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 24px;
    font-size: 0.875rem;
    color: #555;
}
.btn-login {
    width: 100%;
    padding: 12px;
    background: #4f8ef7;
    color: #fff;
    border: none;
    border-radius: 5px;
    font-size: 1rem;
    cursor: pointer;
    transition: background 0.2s;
}
.btn-login:hover {
    background: #2d6ed4;
}

/* ソーシャルログイン */
.social-divider {
    display: flex;
    align-items: center;
    margin: 24px 0 18px;
    color: #999;
    font-size: 0.8rem;
}
.social-divider::before,
.social-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: #ddd;
}
.social-divider span {
    padding: 0 12px;
}
.social-buttons {
    display: flex;
    flex-direction: column;
    gap: 10px;
}
.btn-social {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 11px 12px;
    border: none;
    border-radius: 5px;
    font-size: 0.9rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: opacity 0.2s;
}
.btn-social:hover {
    opacity: 0.85;
}
.btn-line {
    background: #06c755;
    color: #fff;
}
.btn-twitter {
    background: #000;
    color: #fff;
}
.btn-google {
    background: #fff;
    color: #333;
    border: 1px solid #ddd;
}