Wow I was actually pleasantly surprised by this game! It is very well made and really fun!
I love how you can actually change the path using your towers, it's a very unique mechanic that I haven't seen in a TD game, until now! However I do wish that there was an upgrade that made you able to place down walls, so that you don't have to put towers in unnecessary places (where they can't reach) just to get the path in the position that you want it in. Also, it'd be great to have an option to 'check' the cards so the text gets closer and easier to read for those who have trouble reading small text, luckily I've been blessed with good eyesight, but not everybody has that so that's something you might wanna consider too.
Sometimes the splash upgrade became very inconvenient (you can't really use it on the first level without taking damage, so it's a bit in the way). And at one point, I only got upgrades and no towers at the first round of one level, I don't know if that is a bug or what, but I think that needs to not happen.
My favourite tower is the sniper tower :v
and the shield upgrade is bombb