Just move the mouse around. This will always point towards the middle of the screen. If you like this: https://scratch.mit.edu/discuss/topic/123032/ Also, check this one out, cuz it's better. https://scratch.mit.edu/projects/87161928/
The arrow points towards the middle by using Trigonometry. I wanted to make this block because I want to reduce the number of sprites in a project that I am working on. Look inside, this doesn't just use the plain old "point towards" block Feel free to use this block whenever you want, no credit required.