Create a radial stimulus that looks like moving forward

[Michael]

Like this?

Zooming In/Out of Stimuli

I’m programming a variation of an approach/avoid task in which after participants have made a response, the stimuli either increases or decreases in size. I have an idea of how I might do this based on a key press, but I’d like the stimuli to change size after a certain duration of time has passed instead of the key press (to ensure continuity). I was wondering if anyone has done this before or has any advice?