This game is really cool!! (get it? because of the ice, hehe)
The spritework is really good, it's cohesive and serves perfectly for the chosen aesthetics. The music is great too, it stablishes the environment really well, I could listen to it so much time. The gameplay is easy to understand and goes really fluid. The difficulty is high but fair, that's something really hard to achieve. The upgrade system keeps the game diverse and evolving, but I think it's a bit slow.
Sometimes, older games used to restart the game from the beginning when you loose. In terms of difficulty, that's still fair, but it's certainly tedious. The point is that I think it's contradictory to use that system when there's a password to go back to the same part of the game. There's no reason to restart from the beginning if you can use the password, it only makes the player to loose time. If the player wants to retry, it would be better just to start from the same round you lost and just use a password if wants to continue later.
Really great entry, I appreciate the charisma and the gameplay, great job!