Question: How do I make a point on a chart move as I drag a slider control?

I wote a command that creates a plot with a single point:

plots[pointplot](a*[1, 1])

Before hitting Enter I called the context menu and chose Explore. As I change the parameter a the point remains fixed in the picture but the scales change. I wanted the opposite: the scales should stay fixed and the point should move. How can I do this using Explore or in some other way? I would like to see the point move as I drag a slider control.

Thanks for the help.

 

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