Use the up/down arrow keys to change mode (move, create and remove). Press space to render the curve. Use the mouse to: create new points, move points, remove points, and adjust the nth point slider (how far along each line the next point is). There is a maximum of 15 points to prevent too much lag from long calculations.
How it works: it takes the nth point (where n is a percentage between 0 and 100) between 2 consecutive points and generates a new point. It the repeats this for the new points, and again until there is only one point left. By changing the nth value, this last point moves from the start to finish point, influenced by all the points in between. I made this as it was inspired by some maths I've been doing (work on statistics).