I liked it, it doesnt need anything except more lvls and a bit more depth. Many games ask for strategic thinking, noticing details, good reflexes & secure moves, etc... this one asks for patience. :) Imo it's well-made.
Games with good upgrade systems stand out more than those with bad, boring & too short ones. This was fun game :) but upgrading is part of the fun to me at least
Luck-based in a way, but really well-made imo. For a simple flash game, really entertairning, and forcing you to be sometimes overcautious, while sometimes taking advantage of even a slightest chance.