Most technical feedback I received (and I complained about that myself!) was the tile turning mechanic. Kianga came up with the idea to make tiles turn into different directions depending on where you tapped. That works quite well, if you're on a large phone. On a 4-inch display or if your cat is playing, not so good.
But if you play a while it feels much more interesting than having the tile turn into one direction only. The later levels even make it somewhat mandatory to carefully plan your next steps or you might zap a chili. The alternative is having to tap the tiles 5 times if you want to turn it only 60° into one direction. Main issue is, how do you get players to try it out instead of raging that the tiles have a life of their own? Probably not by forcing them to accept one way (remember: I know what's fun!).
So for the final release we added a button to the interface that toggles between two modes and defaults to both directions. Give the default a try though, it makes the puzzles much more interesting and will feel naturally after a while. It's also the only way to beat the challenge modes where you need to avoid needles turning of the tiles.
Speaking of the challenge mode. That's what the star icon is for. Each level has a minimum number of turns it can be solved in. If you stay below or at that number you'll get the star icon on the level chooser screen. I found it interesting that many players where quite fixed onto the star where I only added it as an optional mechanic for the most dedicated. The 50 tile levels should be very hard to achieve the star, short of almost impossible combined with the chili haze. But it's called challenge mode for a reason!