Change the "setting" value for different things to be drawn. Setting 1: Takes in your mouse x and y position and uses them as the inputs for polar coordinates (the mouse x is used for the theta and the mouse y is used for the r), and the resulting point is plotted on the circular grid. Setting 2: Takes a "line" in polar coordinates (r = m*theta + b) and draws it on the circular grid. Setting 3: Takes your mouse's x and y position and (in the same manner as setting 1), uses them as values for theta and r, respectively. Those values for r and theta are then taken and used as the center for a "circle" in polar coordinates ( (r-r_0)^2 + (theta-theta_0)^2 = radius^2 ). The circle is then displayed on the circular grid.
The basic idea I had which led to this was essentially related to taking polar coordinates and representing them as one would with cartesian coordinates (essentially there'd be a separate axis for theta and r, analogous to how cartesian coordinates use x and y axes, as opposed to one of them being represented via concentric circles and the other one being represented by lines of varying slopes). This project essentially "unwraps" that circular grid into a rectangular grid (like you'd see on the xy-plane), draws the shapes onto that rectangular grid, and then "wraps" the grid back into the circular one, deforming the shapes in the process (which is why the lines and circles that are drawn in this project don't look like lines and circles). Note: Assume that none of the things in this project are to scale with one another. It's likely that the grid is measuring completely different sizes than what the numbers for the various settings would suggest. (For example, the "Circle Radius" in setting 3 is likely not what it actually appears to be on the grid.) Note 2: I realize I haven't done much of anything on Scratch in multiple years. I don't anticipate doing too much on here in the future; this project was mainly just an idea I had this evening and I had no better way of coding it (I've never had enough motivation to go and learn more conventional programming languages).