This program contains a DEF block that allows you to use a single line to draw a basic three-point Bézier curve.
Running the program as-is allows you to place curves on the bottom screen by tapping a start point, and end point, and a deviation point. (I don't think that's the technical term.)
Copy the DEF block into any other program to use GBEZIER like a normal command.
GBEZIER Start point X, Start point Y, End point X, End point Y, Relative deviation X, Relative deviation Y, Color
Start point X,Y
The point on the screen where the curve starts from.
End point X,Y
The point on the screen where the curve ends on.
Relative deviation X,Y
This parameter makes the curve stretch in a given direction. 0,0 will draw a straight line.