I love the idea here, at first I wasn't sure what you were going for from the screenshots but when I started to play it, I realized I should have gotten the idea a lot sooner. I really like the reverse shadow of the colossus concept and the art is really pleasing to go with it too. I definitely think it's a tad too difficult, perhaps starting with just a single opponent at first like Shadow of the Colossus would be a bit better, at least to ease into it.
However there is one big change I would recommend that can be done in 2-4 lines of code and will greatly improve the QoL for the game. I started on the webGL version but found it impossible because right clicking would keep bringing up the web player properties. So I downloaded the game and had a slightly better time there. I'm not sure if it would fully fix the issue but you could try confining the cursor lockstate so that you reduce the chance of player's sending the cursor outside of the game window and clicking on something unintended.