The controls are difficult. All the doors are exactly 1 box wide, so you have to line up really well to get through. Same with getting across bridges and around trees. If you are caught at all, he just stands there and gets hit. I don't know if it's that the obstacles were a little smaller in the real zelda, or the speed was slower, but this was never a problem in the NES version.
There have been some desync issues lately. One player moves, the other doesn't see it, you have to reload to sync up again and by that time you've lost a couple minutes on the clock. It it would ping every 15 seconds to see if the peers were in sync that would probably fix it.
Any game where you want to constantly fire should have autofire. Or at least let me hold the button down to continuously fire. Pressing c each time to fire is annoying and wears on your laptop.
An easy way to show how much material each player has would be nice. For example, if you've exchanged knights and someone is also up a pawn and a rook, it would show a pawn and a rook (if you also show everything that was exchanged, it tends to clutter things up). It helps in evaluating if you want to push things toward the endgame or not.
I thought we were done with non-progressive endurance games when that contest ended. The upgrades don't change the gameplay at all, and I can't even tell what the gun upgrade does. Gets repetitive quickly.
Bug: Playing a game, one of us moved really fast, and the timer is timing the wrong guy. When it's my turn to move, his timer counts down, and when it's his turn to move, mine counts down. Only happened once in 15+ games, but wanted to report it.