That's good stuff. Otherwise for recommendations: Keep the symbols recognizable and simple, especially at earlier levels.
Consider adding the 'infinite symbol (omega)' (the 8 that fell over) for things like: 8/0. Maybe make it like a brick that can't be used.
I think this is more fair than turning stuff into 0 or saying 'overflow' ;)
Add colours for the symbols. Keep the focus on simplicty, I think most people just want to move 3+4=7 etc. and want to enjoy the maze part.
The pinguin and celebration effects are a nice addition! I would like some applause too ;) And a bit more firework.
A pinguin that rotates or jumps a little when finished?
Maybe a princess pinguin at the end of higher tier levels?
Perhaps make the levels 'unlockable', for instance by entering a number that can be obtained by finishing a previous level.
Consider bronze (>50 steps), silver (30-50 steps) and gold (<30 steps) for levels as a reward, this will motivate some players to find the 'perfect' solution.
My penguin moves quickly at first. However, after a celebration or when I held the button a little longer he moves slowly and sluggish somehow. Perhaps this needs attention. I think you got a great concept.