Code that I'm stuck with

It's very hard to see in this image due to the bold, bright colours which I will not be using for the finished code! But there is a green dot in the middle of the blue square (background.) The green dot is currently just moving back and forth on that horizontal line.
I have used an if statement to do this but I can't figure out how to then make it go into other directions.

I want the dot to "swim" around acting as a tadpole. It therefore needs to zig zag ad change it's swimming direction all acroos the screen and not just in vertical and horizontal movements. I would like the tadpole to curve around in it's movements to create a more tadpole like behaviour.