// ==UserScript==
// @name         OJ圆角
// @version      1.0
// @description  感谢UID为1032的HhF03提供代码支持，感谢！
// @author       HelloWorldForGao
// @match        *://oj.hetao101.com/*
// @match        *://match.hetao101.com/*
// @match        *://hydro.ac/*
// @match        *://laoda24.vip/*
// @icon         https://hydro.ac/favicon-32x32.png
// @grant        none
// @connect      *://oj.hetao101.com/*
// @connect      *://match.hetao101.com/*
// @connect      *://hydro.ac/*
// @connect      *://laoda24.vip/*
// ==/UserScript==
const a = document.createElement('style');
a.innerHTML = `
.section{
    border-radius: 10px;
}
.button, .dropdown .menu{
    border-radius: 10px;
}
body{
    font-family: -apple-system, BlinkMacSystemFont, "San Francisco Display", "San Francisco", "Helvetica Neue", "Noto Sans", "Noto Sans CJK SC", "Noto Sans CJK", "Source Han Sans", "PingFang SC", "Segoe UI", "Microsoft YaHei", sans-serif;
}
.user-profile-badge{
    border-radius: 7px;
    box-shadow: 0px 1px 3px #656565;
}
data-tooltip, .data-tooltip, span.time.relative.tooltip{
    border-radius: 10px;
}
input.textbox, textarea.textbox, time relative tooltip drop-target drop-element-attached-bottom drop-element-attached-center drop-target-attached-top drop-target-attached-center{
    border-radius: 10px;
}
.search>input{
    border-radius: 10px 0px 0px 0px;
}
.search>button{
    border-radius: 0px  10px 0px 0px;
}
.bp4-tag.bp4-minimal:not([class*=bp4-intent-]){
    border-radius: 10px;
}
.problem__tag-link, .select-container.compact .select, .select.compact{
    border-radius: 10px;
}
pre[class*=language-], .autocomplete-wrapper{
    border-radius: 10px;
}
.section__table-header{
    border-radius: 10px 10px 0 0;
}
div.code-toolbar>.toolbar>.toolbar-item>a, div.code-toolbar>.toolbar>.toolbar-item>button, div.code-toolbar>.toolbar>.toolbar-item>span{
    border-radius: 0 0 0 10px;
}
.contest-sidebar__bg {
    border-radius: 7px 7px 0 0;
}
blockquote {
    border-radius: 7px;
    box-shadow: 2px 3px 3px #aaa;
}
`;
document.head.append(a);

的确弃用了

"偏好设置" 中提供了圆角插件, 但是别的好像没有?