I don't think the game works in browser. I can't get out of the build menu
Normally [TAB] would put you in an out of the build menu, just tried it out and for me that seems to still work :>
Though if that also doesnt work for you im sorry :/
Edit :
Just came to my mind that you might not be able to exit the build menu because of the costs of your build blocks (shows you at the top right)
Lemme know if that works for you!