Well it's fun but kinda hard cause there isn't a lot of explanations.

The units:
It was a bit hard to understand how everything works, but it's normal since it's like a prototype and you don't have time to waste on tutorial :) At first I was just clicking everywhere ^^  I 'm still not sure how mana works.

I like the units but the magician and the archer seem really similar. Plus I'd love to choose wich unit I'm buying. Or have more units waiting behind the gate. I dunno, more freedom certainly about these tiny guys. Maybe more different units ? Like someone building tiny walls or traps, some creative stuff for more choice in the gameplay.

The canon:
No idea how it works, I had to wait to buy all its updrades to see him works. Lazy canon.

The rythm:
Well the start is a bit brutal without explanations, the difficulty could increase with time or maybe with the dstruction of the gates. The game could be a bit faster I think, everything's a bit slow. Or maybe I just needed an option for a faster time.

The interface :
It's clear and simple, I love it ^^ Everything's at the right place. I'm not sure about the shortcuts for the powers since the game seems in an early state. Playing with mouse only was enough for me. About the canon's icon in the middle of the screen, I don't understand its effect, it's messing with the units behaviors for me.
At first I wasn't sure which player I was actually, the interface doesn't show anything about the player's side.

The terrain :
It's again simple and really explicit, I guess a lot of creative and cool backgrounds can be done with this composition ^^

The fun :
It is fun and promising, the gameplay is really easy to understand and I'm sure a ton of cool stuff will be done with it.
I'm not really fan of the lowpoly style, it's my personnal taste and maybe this is just because of the ongoing state.
Oh ... you should write more infos on the project's page !

Thanks for the work on your game, it seems really promising to me !