I liked the demo a lot. The AI is competent enough to do some serious damage if you're not careful, and I had fun coming up with the most strategic placement of my units for the most amount of damage.
This has serious potential, I'm looking forward to see where this goes. I think it would benefit from a little UI work to match the game's aesthetic, and some shortcuts that don't require me to move my hand as far. If there was an ending, I didn't see it. After killing the last goblin mage on a map, I passed the turn and got hit by the late goblin's electric attack, then after that it automatically passed the turn back to me. Some kind of victory screen would be nice. Also, a minor note: It seems like going through water didn't affect how far you could move, when really it should slow you down to at least half the distance you'd normally go.
Overall, very impressed. I'm excited to see where this goes!