All the components needed to be big enough for eye tracking "selection" to consistently work. It's frustrating when you are trying to look at a button to press, but the eye tracking thinks you are looking elsewhere. If the screen were any small, the components wouldn't fit. I believe the dimensions should work on most computer screen sizes and just bar out mobile devices. This was also intended since the eye tracking does not work on mobile.
I'm glad it feels natural! I wanted it to feel similar to Apple vision pros where the eye tracking just works. Hopefully in the future, I can just curl up in a blanket and let my eyes do all the scrolling when I'm reading.
Thanks for your interest! An eye tracking game is an interesting concept. My concern is that there is already a lot of overhead used for eye tracking that an entire game on top of that would be too laggy to be playable. Also, the eye tracking software right now doesn't seem precise enough for things like aiming. I could totally see a pure standalone game that utilizes eye tracking.
1 - I experimented with some calibration involving staring at a point, but I found it troublesome as blinking would make lead to some inaccurate calibration data (webgazer doesn't have blink detection). It was also a little more fatiguing since the user would have to really focus on staring the entire time. I found that it was less mentally fatiguing if the user could control their own calibration give themselves room to blink or just rest their eyes for a second.
2 - Ghost overlays is a really good idea. I'll see what I can do to implement that feature.
I really appreciate you taking your time to write this!