I'm a big fan of chess puzzles so this game is interesting to me.
Mechanically it's quite solid and leaves a lot of design space open for different challenges like enemies that change their threat areas on each move, ways to manipulate enemy positions, or new ways for your characters to move.

However I had some difficulties with the visual side that prevented me from enjoying the game.
Light green and light blue are very hard to tell apart and was starting to give me a headache once I got to enemies with both robot and spirit attack spaces. Changing the hue or the brightness would help tell the two types of danger apart at a glance with little effort. In the future, as the attack ranges are such an important part of the game play, it may be worth developing different art assets for the different dangers. Targeting reticle or electric wires for robots, runes or ghostly hands for spirits.
A similar effect can be found when the two controllable characters get close as the yellow of the lantern, the light on the floor, and the orange-ish of the robot all start to bend into each other and become a visual mess, which is a shame as the sprite work is quite nice otherwise. Consider borders around sprites, differentiating of colors/values.
Some greater feedback for character selection would be nice. The feint yellow box below them is hard to see on some spaces so a confirmation sound from the unit, like you can hear in may RTS games, or a quick animation would guarantee I know who I have selected and will prevent accidental moves.
It's a minor point but on the dialogue boxes an "A" in a circle made me think it needed a controller rather than hitting the "A" key. Either putting it in a box to better indicate a keyboard or allow other input like space or left click to also cycle through dialogue might be good.

I'm seeing a lot of potential here, though. Keep up the good work!

Overall, the game has promise. From what I was able to play, I had fun. I agree with what Oles said, so I'll just add onto it.

The main problem I ran into is the game seems to crash randomly after attacking an enemy. It was never consistent, but the new enemy introduced 4 or 5 levels in would always crash the game. Needless to say, I wasn't able to finish the demo because of it.

Overall, I though the mechanics worked well, but I did find it kind of odd that you had to go into a specific square (their back) to attack instead of just occupying the square they're on. It's not a deal breaker, but It does feel a little arbitrary and a bit of a lazy way to enforce certain setups. The spirit can't hurt the lantern, so why go behind for a sneak attack?

Visually, the game looks great, props for the art! But, I did have some issues with game-play related feedback. I think the main reason is the relatively small game area on-top of an already small resolution, making the spirit enemies hard to differentiate, and making their silhouettes harder to make out at a glance. I'd get sniped thinking I was out of range of the sword, but it turned out it was I was looking at an archer.

All in all, I look forward to seeing the game once it's polished up and expanded. Nice work so far!