Fenomenal, the game surprised me in a very good way.
Such a simple game but very well polished.
Maybe the music could receive some upgrades, but the gameplay and game design were really nice.
I managed to finish the game on my first run, and I don't even know how much I spent playing.
The idea of having the upgrades eaten through a Tetris-like mechanic is not new, but you made it feel really good.

Maybe there are a few upgrades that allows the player to become a bit too strong ?!
Yet, even that works fine, as a player I love the idea of believing "I managed to break the game" even if it's for a little.
But you balanced it well with the portals and stronger enemies.

Great job !