Gemini UI Deep Customization (Smooth Native Animations)

Sets chat width and sidebar width. Overrides native CSS variables to keep animations smooth, plus font and nav item tweaks.
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// ==UserScript==
// @name         Gemini UI Deep Customization (Smooth Native Animations)
// @name:zh-CN   Gemini 界面深度定制（保留原生动画顺滑版）
// @namespace    http://tampermonkey.net/
// @version      1.0.0
// @description  Sets chat width and sidebar width. Overrides native CSS variables to keep animations smooth, plus font and nav item tweaks.
// @description:zh-CN  修改聊天宽度、侧边栏宽度。劫持原生 CSS 变量保留动画顺滑，并调整字体与列表项高度。
// @icon         https://www.gstatic.com/lamda/images/gemini_sparkle_aurora_33f86dc0c0257da337c63.svg
// @author       Joe_Ye
// @license      MIT
// @match        https://gemini.google.com/*
// @run-at       document-start
// @grant        none
// ==/UserScript==

(function () {
    'use strict';

    const css = `
        /* 1. 聊天对话区域：修改为固定 1000px */
        .conversation-container,
        div[class*="conversation-container"] {
            max-width: 1050px !important;
            width: 100% !important;
        }

        /* 2. 全局注入侧边栏的 CSS 变量，让所有组件都能读取到 */
        /* 原生收起宽度为 72px，所以新的差值 (diff) 是 500 - 72 = 428px */
        :root, body, bard-sidenav, bard-mode-switcher, top-bar-actions {
            --bard-sidenav-open-width: 380px !important;
            --bard-sidenav-open-closed-width-diff: 308px !important;
        }

        /* 3. 修复顶部栏展开时的位置 */
        /* 利用原生的 .side-nav-expanded 状态类，不破坏收起时的状态 */
        .side-nav-expanded,
        [dir="ltr"] .side-nav-expanded {
            left: 380px !important;
        }

        /* 4. 修改指定字体大小和列表项高度 */
        .gds-emphasized-body-s {
            font-size: 13pt !important; /* 选中项 (已修复注释格式) */
        }

        .title-text.gds-body-s,
        .gds-body-s,
        .title-text.gds-emphasized-body-s {
            font-size: 13pt !important;
            line-height: normal !important; /* 禁用并重置原有的 line-height */
        }

        :not(.is-mobile) .gem-nav-list-item.gmat-override {
            height: 45px !important;
        }
    `;

    const injectStyle = () => {
        if (document.head) {
            const oldStyle = document.getElementById('gemini-custom-fix-v6');
            if (oldStyle) oldStyle.remove();

            const style = document.createElement('style');
            style.id = 'gemini-custom-fix-v6';
            style.textContent = css;
            document.head.appendChild(style);
        }
    };

    injectStyle();

    const observer = new MutationObserver(() => {
        if (document.head && !document.getElementById('gemini-custom-fix-v6')) {
            injectStyle();
        }
    });

    observer.observe(document.documentElement, { childList: true, subtree: true });
})();