Very boring. You have to click on all the characters individually multiple times and it feels like your whole game session goes into clicking on the different characters to try to level them up. There's no option to just do an automatic upgrade and then you can just check whatever characters you want to do it if you want to do it in bulk or whatnot. Lots of currencies to keep track of and there's never enough XP even if you buy some from the shop so forget it. Endless upgrading.