I love Pico-8 but I have to say this:
The mobile controls for the HTML Player are really awful in my opinion. They work, but I feel I don't play as well with them due to a lack of responsiveness.
Personally, I think a simple glow for parts that are being touched, button sounds or minor haptic feed back would definitely be an improvement. But overall it's kind of a shame how basic they look compared to how stylized the rest of Pico-8 looks, almost as if they were an after thought. I hope that when Pico-8 eventually comes to Android and iOS natively that the entire interface has as much love as the Pico-8.