It'd be really cool if you could respec your abilities, it would make it so much easier to experiment with skills. I absolutely loved the game, and really got into building the 'perfect deck'. I tried a single sword, with rest teleport, but that couldn't work out on an early level, which is why I wish I could respec, so that I could build up my arsenal without worrying about dying on early levels with experimental decks. Also, the grenade felt really underpowered, to the point of being useless. The levels also felt pretty tight, and at one point, a single wrong upgrade screwed me over (why'd I upgrade the sniper, I needed sword!) All that criticism may not sound too friendly towards the game, but I seriously loved it. The sounds, the strategy, even the minimalist graphics, all played a part in making that awesome experience. Good job, I only wish that I found the end.
P.S. I just had an epiphany. What if you could see the next level whilst preparing? Add in some foresight to the game, and you've got some deep strategy to really sell the puzzle!