* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 16px;
    background: #f0f2f5;
    font-family: Arial, "Microsoft YaHei", sans-serif;
}

.login-box {
    width: 100%;
    max-width: 400px;
    padding: 40px;
    background: #fff;
    border-radius: 8px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, .08);
}

.login-box h2 {
    margin-bottom: 30px;
    color: #333;
    text-align: center;
}

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

.form-group label {
    display: block;
    margin-bottom: 6px;
    color: #666;
}

.form-group input {
    width: 100%;
    height: 42px;
    padding: 0 12px;
    border: 1px solid #d9d9d9;
    border-radius: 4px;
    outline: none;
    font-size: 14px;
    transition: border-color .2s, box-shadow .2s;
}

.form-group input:focus {
    border-color: #1677ff;
    box-shadow: 0 0 0 2px rgba(22, 119, 255, .15);
}

.btn {
    width: 100%;
    height: 42px;
    border: 0;
    border-radius: 4px;
    background: #1677ff;
    color: #fff;
    cursor: pointer;
    font-size: 16px;
}

.btn:hover {
    background: #4096ff;
}

.btn:focus-visible {
    outline: 2px solid #1677ff;
    outline-offset: 2px;
}

.btn:disabled {
    background: #91caff;
    cursor: not-allowed;
}

.error-msg {
    margin-top: 12px;
    color: #d9363e;
    text-align: center;
}

.error-msg[hidden] {
    display: none;
}

@media (max-width: 420px) {
    .login-box {
        padding: 32px 24px;
    }
}