Linux user here.
It seems to work well. Graphics are simplistic but it's easy to see what's what. I like that I have one of each type of pony on my side; though my pegasus doesn't seem able to fly. (I'm not quite sure how flight should be handled; I see that he seems to ignore obstacles, but flight might also give him the ability to hover over the battlefield and taunt everyone who didn't bring ranged weapons or the ability to fly, surely? Of course, he'd have to come down into melee range in order to attack, and if the first attack on any unit in a given round permits a counterattack (assuming the unit survives the attack), then a flying pegasus is not completely invulnerable... that also would make dogpiling on a single unit a better strategy, as it only gets one counterattack... of course, an alicorn would be able to both fly and attack at range, a deadly combination, but alicorns are overpowered anyhow...)
The unicorn has a good set of abilities, a ranged attack and a short-lived bubble shield.
A weakness in the enemy AI; if you attack once and then Dash away to the limits of your movement, then the enemy can catch up to you but can't attack. (I used that to defeat the entire tribe of Timberwolves with one earth pony after my other two ponies were ignominously defeated early). The usefulness of this strategy would be significantly reduced if melee defenders could counterattack (see above).
The shield and defense actions are useful, but not nearly as useful as running away (see above paragraph).
The randomness in when the opponent gets KO'd seems a bit too much to me (it's frustrating when timberwolves at -5 and -8 are still standing, but an earth pony at -1 goes down). I see what you're getting at but I think it would work better if it was a bit less random (say, double the odds of KO'ing a given pony). It rewards skill better if the results of a given move are more predictable, after all.