Lives system is not a good idea for a trial and error platformer, works great as a single player experience though the two player option is still a neat touch.

This is a good concept, however the lives system needs to go as most of it is trial and error.
Also this definitely feels better as a 1 player ambidextrous game than as a 2 players game.

I have a lot of problems with the mechanics in this game. The one thing that I try and present when I review a game is: "Frustrating does not equal challenging".

There are four overall elements that embody this for me:
*A lives system in a puzzle platformer
*You are reset to the beginning of other levels when you lose all your lives
*If you go on to the next level and lost any lives, you never get them back unless you reset with level select or start over

Seriously, one of the most frustrating things you could do to a player is to mitigate any progress on the puzzle they just made attempts at understanding by having them go back through one they just completed (thank god there's a completely unlocked level select).

You have some interesting puzzles/mechanics here, but those 2 mechanics alone drain a lot of the fun someone would be having solving the puzzles you've given them. You're essentially punishing the player for guessing something incorrectly (or even in some cases, like in level 2 with red's lever dropping the platform on the unsuspecting player, by them completely not expecting some mechanics. It'd be funnier/less frustrating if the lives system wasn't there).

The only reason this rating isn't any lower is because you have an open level select.
Just imagining having to unlock these levels one by one, or playing through a 15-20 level pack.

Edit: I look forward to any changes, and I hope that something like this can expand into a fun project to work on.