Issy is a barebones startpage intended to have minimal features and be easy on the eyes. It features a real time clock, Google search bar and a hidden menu of links.
Homepage
Ctrl+L > about:preferences > Home Page > Enter the HTML file location.
New tab
Install the New Tab Override extension > Ctrl+Shift+A > Extensions > New Tab Options > Enter the HTML file location.
Homepage
Settings > Show Home Button > Change New Tab > Enter the HTML file location.
New tab
Install the New Tab Redirect extension > Settings > More Tools > Options for New Tab Redirect > Enter the HTML file location.
Search the style.css file for the listed colors:
Main background color: #212121
Search background colors: #151515, #000, #111
Text color: #eee, #fff
Submit an issue if you have any problems.