Bug:
If you are a little low on gold at hand and move your mouse over the “buy hero levels” (so the “buy 5” shows up on all your showing heroes) and then quickly buy all heroes their 5 levels, you can end up with a negative amount of gold at hand.
I guess this only happening because i buy the 5 levels too quickly (before they disappear from showing)
Another thing that would be nice in this game: being able to buy several main character levels at once (more than 5 per click); i start a new day with several millions of gold, and can buy over 1000 main character’s levels at once