Thanks for playing!! ^_^
Yeah if you're familiar with the genre, you'd probably wanna switch to Hard pretty early on I guess ^_^" I might add a way to detect if the player is beating the game too easily and offer them to up the difficulty at the end of levels.
You can increase the amount of cats you can place with the bottom-most upgrade but I guess overall it's quite limited yeah.
What do you mean by placing upgrades directly on the board? By the way, were you aware you can upgrade the cats you place by left clicking on them? Once they reach lvl 10 they can upgrade into one of two types with left or right click. (Archer -> Mage OR Crossbow). When I update the game though I'll add probably a third base type, but the idea is really that they branch off as you upgrade them.
Thanks again for playing and taking the time to leave detailed feedback ^_^