:root {
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --background-color: #121212;
    --surface-color: #1e1e1e;
    --on-surface-color: #e0e0e0;
    --on-surface-color-muted: #a0a0a0;
    --danger-color: #dc3545;
    --border-color: #333;
    --box-shadow: 0 4px 20px rgba(0,0,0,0.5);
}

.login-container {
    width: 100%;
    max-width: 420px;
    margin: 50px auto;
    padding: 40px;
    background-color: var(--surface-color);
    border-radius: 15px;
    box-shadow: var(--box-shadow);
    text-align: center;
}

.login-container h2 {
    margin-bottom: 30px;
    font-size: 2rem;
    color: #fff;
}

.social-btn {
    display: block;
    width: 100%;
    padding: 15px;
    border-radius: 10px;
    border: none;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    background-color: #4285F4;
    color: white;
    margin-bottom: 25px;
    transition: background-color 0.2s;
}
.social-btn:hover {
    background-color: #357ae8;
}

.divider {
    font-size: 14px;
    color: var(--on-surface-color-muted);
    margin: 25px 0;
    display: flex;
    align-items: center;
    text-align: center;
}
.divider::before, .divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid var(--border-color);
}
.divider:not(:empty)::before { margin-right: .75em; }
.divider:not(:empty)::after { margin-left: .75em; }

.login-container input {
    width: 100%;
    padding: 15px;
    margin-bottom: 18px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
    background-color: #222;
    color: #fff;
    font-size: 16px;
    box-sizing: border-box;
}

#error-message {
    color: var(--danger-color);
    margin-bottom: 18px;
    font-size: 14px;
    min-height: 18px;
}

.button-group {
    display: flex;
    gap: 12px;
}

.auth-action-btn {
    flex: 1;
    padding: 15px;
    border: none;
    border-radius: 10px;
    background-color: var(--primary-color);
    color: white;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    transition: background-color 0.2s;
}
.auth-action-btn:hover {
    background-color: var(--primary-hover);
}

.back-link {
    display: block;
    margin-top: 30px;
    color: var(--on-surface-color-muted);
    text-decoration: none;
    font-size: 14px;
}

.back-link:hover {
    text-decoration: underline;
}