// ==UserScript==
// @name         non-rounded thumbnails
// @version      1.0
// @description  non-rounded thumbnails
// @author       alfie
// @match        *://*.youtube.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    const customStyle = `
        ytd-thumbnail[size=large] a.ytd-thumbnail,
        ytd-thumbnail[size=large]:before {
            border-radius: 0 !important;
        }
    `;
    const styleElement = document.createElement('style');
    styleElement.type = 'text/css';
    styleElement.textContent = customStyle;

    document.head.appendChild(styleElement);
})();