Five-point conic
Five distinct points determine a unique conic section of the form Ax^2+By^2+Cxy+Dx+Ey+F=0.
To start playing with this, move around point A. This will keep the conic non-rotated and centered at the origin.
Feel free to move around any of the points.
To set a point to a specific coordinate, type (for example) "A=(1,2)" in the input bar at the bottom and hit enter.
To re-set the drawing, click on the re-set arrows in the upper right corner.