/* ============================================================
   响应式导航（工程圈 / 安培考试 网站）
   三端显示策略：
   - 电脑端  (>992px) ：完整横向菜单
   - 平板端  (769~992)：横向紧凑菜单（缩小间距/字号）
   - 手机端  (<=768px)：汉堡图标 + 下拉菜单
   本文件统一覆盖各页原有的 nav 媒体查询，避免菜单挤压/隐藏无替代。
   ============================================================ */

/* 汉堡按钮：默认隐藏（电脑/平板不显示） */
.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 5px;
    width: 42px;
    height: 42px;
    margin-left: 8px;
    padding: 0;
    border: none;
    background: transparent;
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
}
.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: #333;
    border-radius: 2px;
    transition: transform .25s ease, opacity .2s ease;
}
/* 展开时变成 X */
.nav.nav-open .nav-toggle span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav.nav-open .nav-toggle span:nth-child(2) { opacity: 0; }
.nav.nav-open .nav-toggle span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- 平板端：横向紧凑 ---------- */
@media (min-width: 769px) and (max-width: 992px) {
    .nav { padding: 0 24px !important; }
    .nav-links { gap: 18px !important; }
    .nav-links a { font-size: 14px !important; }
    .nav-login { padding: 7px 14px !important; font-size: 13px !important; }
}

/* ---------- 手机端：汉堡 + 下拉 ---------- */
@media (max-width: 768px) {
    .nav-toggle { display: inline-flex; }

    .nav-links {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        align-items: stretch;
        gap: 0;
        background: #fff;
        box-shadow: 0 10px 24px rgba(0, 0, 0, 0.12);
        padding: 6px 0;
        max-height: calc(100vh - 64px);
        overflow-y: auto;
        /* 默认收起 */
        display: none;
    }
    .nav.nav-open .nav-links { display: flex; }

    .nav-links a {
        padding: 14px 24px;
        font-size: 15px;
        width: 100%;
        box-sizing: border-box;
        border-bottom: 1px solid #f0f0f0;
        white-space: nowrap;
    }
    .nav-links a:last-child { border-bottom: none; }
    .nav-links a.active {
        background: #f0f6ff;
        color: #1a56db;
        font-weight: 600;
    }

    /* 登录按钮在手机端变成整行按钮 */
    .nav-login {
        margin: 10px 24px 14px;
        text-align: center;
        display: block;
        border-radius: 6px;
    }
}