Thank you for this wonderful little game. The music was nice and relaxing and didn't get too repetitive. My first playthrough took me a bit over an hour (although when I finished, it said 43 minutes, but that may be because I quit and reloaded the game when I got stuck).
I found that performance (on a Mac) with Intel HD graphics (2018 Mac mini) was pretty slow. I didn't expect it to be wonderful, but it felt like I was moving through honey at times. I ran it 1280 x 720 in a window and found I had to have it on High as the janky shadows on medium really spoiled the look of the world.
** Potential Spoilers below **
Some of the things that I got stuck on:
1. I accidentally dropped the key at the start, and then couldn't find it again. I'm not sure how I dropped it, but I looked around and couldn't see it. I had to quit and reload to get back on track.
2. It took me a while to figure out that after placing the sun cubes in order that I could then go outside again.
3. I worked out the plank fairly quickly, but mainly because I accidentally read a spoiler here. As so few other elements in the environment are able to be interacted with, it would have taken me quite while to try and do something with it. One thing I did naturally try was to walk up it. Maybe if you run into it, it could get bumped, make a noise and rock around a little bit, giving a hint that it's not just static scenery?
4. The colours at the end required a bit of guesswork, but all the hints were there.
** /spoilers **
In terms of general UI/UX - it would be very handy to navigate the menus in the game with the arrow keys and use space/enter to activate menu items. When I brought up the menu in game, I sometimes wasn't able to select anything from the menu, so had to quit and relaunch the game.
With the cards, it's fine to have them brought up with Tab, that works very well for me however my natural inclination is to then hit Esc to get rid of them. This instead brought up the menu.
All in all however a quite enjoyable snack of a game. Thank you for all your hard work.