I very much enjoyed it, completed the whole demo. A lot of good stuff, I felt that the difficulty curve was good, and it felt satisfying to put it together in the final battle. A couple of things to think about:
The most glaring thing has to be the mixels. It just looks so distracting. You could maybe get away with the characters being a different pxiel size if you must, but having the roads and buildings being different from the grass and rocks is a step too far. You could just scale up/down assets sizes and it would be a big improvement, even without any cleanup.
The white objective text blends in to the snow white backgrounds, maybe put a border around it.
The buying units menu was a bit unintuitive, I think there should probably be arrows to slide through the units, rather than having to click on the portraits of the left or rightmost unit to scroll through them. The 'buy' button probably shouldn't have grey text either, it makes it look like tis greyed out.
The amount of gold I got far outpaced the amount I needed, unless I missed some way to restock the shops, or increase my unit cap from 3.
The level where you have to learn the spells was a bit boring, maybe you could come up with another way to teach each one in a specific situation, rather than just casting them, then waiting a turn each time.
A few times the text didn't load. Once when talking to the loli when we were being chased, then when the evil hooded figure showed up at the end and the elven archer started talking.
As a final thing, I wonder if anything could be done to speed up the turns, such as allowing us to move multiple units at once, or shortening the time in between turns. i know a lot of the time things like this can hard to change, but I think it would go a long way to make it more snappy.
I hope I don't sound too critical, this is the only demo I've played for a significant amount of time this dd, so you must've done something right to keep my attention. Good gameplay loop!