1) Main menu UI scaling seems to be off. Text was so small, it was unreadable in the WebGL build.
2) WebGL build forcing fullscreen did not work, perhaps introduce a fullscreen button?
3) If you hold down LMB before interacting with an object that shows dialogue, you can trick the game into thinking you are holding down LMB permanently.
4) It looked like a nice terraria/minecraft cave exploring setting. Sadly you cannot die, therefore once you commit to going down, you inevitable need to make the journey to the top which can take a while.
5) Mining seems tedious due to the long time needed to break blocks (if there are upgrades ignore this).
6) The tutorial was pretty nice, not too intrusive and made sense within the game context.
7) First time teleporting was a bit jarring, perhaps with some visual effects this could be better telegraphed.
8) Small icons are great when the player knows what it all means. As a new player a bit more zoomed in gameplay would go a long way towards building familiarity.