* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Microsoft YaHei', 'SimSun', sans-serif;
}

body {
    background: linear-gradient(135deg, #f5f7fa 0%, #e4edf5 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.login-container {
    width: 100%;
    max-width: 480px;
    background: white;
    border-radius: 15px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.15);
    overflow: hidden;
}

.login-header {
    background: linear-gradient(135deg, #1a56db 0%, #2d6a9c 100%);
    color: white;
    padding: 35px 30px;
    text-align: center;
}

.login-header h1 {
    font-size: 2.2rem;
    margin-bottom: 10px;
    font-weight: 700;
}

.login-header p {
    font-size: 1.1rem;
    opacity: 0.9;
    letter-spacing: 0.5px;
}

.login-form {
    padding: 35px 30px;
}

.form-group {
    margin-bottom: 25px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: #333;
}

.form-control {
    width: 100%;
    padding: 14px 15px;
    border: 1px solid #ddd;
    border-radius: 8px;
    font-size: 1.05rem;
    transition: border-color 0.3s;
}

.form-control:focus {
    outline: none;
    border-color: #1a56db;
    box-shadow: 0 0 0 3px rgba(26, 86, 219, 0.2);
}

.btn {
    display: block;
    width: 100%;
    background: linear-gradient(to right, #1a56db, #2d6a9c);
    color: white;
    border: none;
    padding: 14px;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    text-align: center;
}

.btn:hover {
    background: linear-gradient(to right, #1545ab, #255580);
    transform: translateY(-2px);
}

.footer {
    text-align: center;
    padding: 20px 30px;
    color: #777;
    border-top: 1px solid #eee;
    font-size: 0.9rem;
}

.alert {
    padding: 12px 15px;
    margin-bottom: 20px;
    border-radius: 6px;
    font-size: 0.95rem;
}

.alert-danger {
    background-color: #ffebee;
    color: #c62828;
    border: 1px solid #ffcdd2;
}

.alert-success {
    background-color: #e8f5e9;
    color: #388e3c;
    border: 1px solid #c8e6c9;
}

.switch-link {
    text-align: center;
    margin-top: 15px;
    padding: 10px 0;
    border-top: 1px solid #eee;
}

.switch-link a {
    color: #1a56db;
    text-decoration: none;
    font-weight: 500;
}

.switch-link a:hover {
    text-decoration: underline;
}

/* =========================================
   响应式适配增强版：平板 & 手机
   ========================================= */

/* 📱 平板适配 (≤ 992px) */
@media screen and (max-width: 992px) {
    body { padding: 30px 20px; }

    .login-container { max-width: 460px; }

    .login-header { padding: 30px 25px; }
    .login-header h1 { font-size: 2rem; }
    .login-header p { font-size: 1rem; }

    .login-form { padding: 30px 25px; }
}

/* 📱 小平板 & 大手机 (≤ 768px) */
@media screen and (max-width: 768px) {
    body {
        padding: 20px 15px;
        align-items: flex-start; /* 改为顶部对齐，避免软键盘弹出时内容被遮挡 */
    }

    .login-container {
        max-width: 100%;
        border-radius: 12px;
        box-shadow: 0 10px 25px rgba(0, 0, 0, 0.12);
    }

    .login-header { padding: 25px 20px; }
    .login-header h1 { font-size: 1.6rem; margin-bottom: 8px; }
    .login-header p { font-size: 0.95rem; }

    .login-form { padding: 25px 20px; }

    .form-group { margin-bottom: 20px; }
    .form-group label { font-size: 0.95rem; margin-bottom: 6px; }

    .form-control {
        padding: 12px 14px;
        font-size: 16px !important; /* ⭐ 防止 iOS Safari 自动缩放 */
    }

    .btn {
        padding: 12px;
        font-size: 1rem;
    }
    .btn:hover { transform: none; } /* 禁用 hover 动画防粘滞 */

    .alert { padding: 10px 14px; font-size: 0.9rem; }

    .footer { padding: 15px 20px; font-size: 0.85rem; }
    .switch-link { margin-top: 12px; padding: 8px 0; }
}

/* 📱 手机适配 (≤ 480px) */
@media screen and (max-width: 480px) {
    body {
        padding: 0;
        background: white; /* 手机端移除渐变背景，减少渲染开销 */
        min-height: 100dvh; /* 动态视口高度，适配移动端地址栏 */
    }

    .login-container {
        border-radius: 0;
        box-shadow: none;
        min-height: 100dvh;
        display: flex;
        flex-direction: column;
    }

    .login-header {
        padding: 40px 20px 30px; /* 顶部增加安全区距离 */
        flex-shrink: 0;
    }
    .login-header h1 { font-size: 1.5rem; }
    .login-header p { font-size: 0.9rem; letter-spacing: 0.3px; }

    .login-form {
        padding: 25px 20px;
        flex: 1; /* 表单区域撑满剩余空间 */
        display: flex;
        flex-direction: column;
        justify-content: center; /* 垂直居中表单内容 */
    }

    .form-group { margin-bottom: 22px; }
    .form-group label { font-size: 0.9rem; }

    .form-control {
        padding: 14px 15px; /* 增大触控热区 */
        border-radius: 10px;
    }

    .btn {
        padding: 15px;
        font-size: 1.05rem;
        border-radius: 10px;
        margin-top: 10px;
    }

    .alert {
        padding: 12px 15px;
        font-size: 0.85rem;
        border-radius: 8px;
    }

    .switch-link a { font-size: 0.95rem; padding: 8px; display: inline-block; }

    .footer {
        padding: 15px 20px;
        font-size: 0.75rem;
        flex-shrink: 0;
    }
}