Currently, the only way to change the resolution is quitting, going to the settings, pressing an option, restarting the game, and then boom there you go. I personally think that the ability to just press F11 to go fullscreen would be amazing and a great saver of time, and maybe even being able to just drag the game edges to resolution. If that isn't possible, then make it so when you press F11 you automatically go to 1920x1080. Also, when minimizing the game and re-opening it, it just leaves you with either missing textures or a black, unresponsive, unclosable screen. Would love if that could be fixed.
I know you might think this is outrageous but I play in 800x600 so that I can watch youtube and play cubic castles at the same time. If I ever wanted to record something right then and there, I would have to take about a minute to change my resolution to fullscreen 1920x1080, which is something that should be easily done in 5 seconds (like Minecraft).
Edit: If you get Cubic Castles on Bluestacks, you can drag to resize the game and also easily go into Fullscreen, so it is definitely possible to drag the edges to re-size it and make it fullscreen.