Can someone help me with this ?

I assume you want to set the opacity (0-100) depending on the mouse's coordinate on the screen. The variables indicating the mouse's coordinates are mouseX and mouseY.

To achieve this, you will need to divide the mouseX/mouseY (whichever you choose) by 4 to what's called "normalize" it. If your mouse was at 320 for example... Dividing it by four would give you 80, and this works because the bounds that the opacity can be set to is 0-100.

normalized = mouseX / 4

Circle(mouseX, mouseY, 50, fill='navy', opacity=normalized)

...or if you want to do it in one line...

Circle(mouseX, mouseY, 50, fill='navy', opacity=mouseX / 4)

answer; ///shut the compressor off.