I bought the game and have been having fun poking around and exploring.  I got a few lizards and played with them.  I randomly stumbled upon a boss, the rabbit, and was surprised after I beat the boss, the game ended and started back up from the title.  I was a little surprised by this, expecting the game to want me to beat all the bosses before giving me credits.  Is this the way that the game goes, just finding all the bosses and beating them at your own leisure, in whatever order you see fit?  Also, is there a purpose to the coins?

Or am I just thinking too much about it, and should just enjoy it, and everything will become clear eventually?

It's very open-ended and that can be pretty intimidating, to play without a clear goal from the start. There was a room I discovered after my first boss that pretty clearly indicated how many bosses there are, which can give you a better sense of progression.

I haven't found that room yet.  I'm still going to explore the whole game regardless, and try to get everything there is to get.  Based on the map and going around, I figure there are probably as many bosses as there are unique areas (water, factory, lava, forest, castle, etc), give or take a few.  I was mostly surprised that beating that boss sent me back to the title, which confused me when it comes to the coins, as I thought I'd just collect them as I went.  Now I'm thinking there's a specific purpose of the coins for some particular boss or room (or maybe they might have something to do with the pillars?), since they'd have to be collected in one run, and it seems like the game is meant to be played in multiple runs, rather than a long play.

I'm not trying to get spoiled or anything, just making sure that there's nothing obvious that I missed.  I'm assuming the things that are still mysteries to me are supposed to be until I figure it out.

I finally got around to playing some more, and after 2 more bosses, I finally found the room you were talking about.   Still no idea about the coins or anything, but this is a lot of fun.