In MacOS in fullscreen, you need to double click to select anything until you exit and re-enter fullscreen. When this glitch happens, the mouse cursor is also visible in-game. Exiting fullscreen and re-entering it fixes it but this bug shouldn't be here in the first place. Thanks!
Environment
MacOS Mojave version 10.14
Macbook Retina 12-inch, early 2016
1.1 GHz Intel Core m3
RAM: 8 GB 1867 MHz LPDDR3
I've experienced this bug too.