This short guide will help you fix the “no fullscreen” issue with Blockscape.
Fullscreen Not Showing?
Without getting into all the why’s and wherefore’s, I’m just going to explain how to fix the issue here.
You launch Blockscape, make sure Fullscreen is checked, and the resolution you want. Say, 1920×1080.
You hit the play button, and bam! You end up with a small screen in the upper left corner.
Go to where Blockscape is located and right-click on Blockscape.exe.
Select the Compatibility tab.
Check the box that says, Disable fullscreen optimizations.
Restart the game and enjoy.