I like the concept, and I also appreciate your philosophy of "show don't tell", but a major roadblock to making that learning experience fun is that the death screen and respawn time is far too long, especially when you're dying frequently early on because you still don't know it's who's who in the rock-paper-scissors diagram.
On the topic of your level design, the most intuitive level was the one that had one of each bad guy in a triangle; this instantly made me realize everyone has a strength and weakness, before that level I just assumed that the axe guy kicked everyone's ass because that's all I saw until then. I would actually make that your second level (your first level's a great intro to the controls, no need to change that), since it makes the rest of the learning process flow much easier.
Finally I would change how the red squares work. It was a little confusing figuring out the archer's actual range since the red squares relative to the square you clicked don't actually show until AFTER you've already made the move and realize you're out of range.
Despite my criticisms, this game has loads of potential as a fun $5 steam game, just give it that extra pollish and more playtesting, and I'd buy it!