Super cool game! The design of the units feels very thought out and balanced. I'm not the best at strategy games but at least I never had any turn when the choice of units was obvious, always had to think about what to buy and control the gambler urges to reroll the shop until I got exactly what I wanted (or more probably waste all my mana attempting to).
The graphics for the UI and the units/resources is also simple in a very clean way, they have the exact amount of detail to look good but not be too charged at the same time. I specially loved Coal Nugget, I find them extremely cute >_>
One strange issue I have is that the words "orthogonal" and "diagonal" in the descriptions are mixed up? Don't know if this is some kind of dialect thing or just some silly mistake that slipped by testing but to me orthogonal has always been what the game refers as diagonal and vice versa. I don't want to be pedantic about language but this makes the game a bit confusing, specially because you can't see the icons for the descriptions of the units after buying them.
I think it would be great to show somehow the units that are affecting other units, for example if I select a placed red chest, having the surrounding red summons highlighted would show me at a glance that everything is working as expected and it would make easier for me to evaluate my placements without being super familiar with the units.
Overall I think this is a great game and I kind of want to (and surely will) play it again, great job ^_^