The animation and art in this is incredible! Really well done.
As for the gameplay, it's a bit barebones, as you note, but it reminds me a bit of a fighting minigame in some ship-based pirate game I can't remember the name of. Some more indications of what's going on would have been nice (e.g. HP bar at least for the player, some info about what each weapon does, etc.).
I'll note that "defend" seems pretty meaningless in a random damage situation where you have no way of knowing what the enemy is planning. It basically just delays the turn. (If there were multiple characters or an indication of the enemy's plans, it would be more useful.)
Overall, I liked it, in major part because of the excellent animation. Nicely done!