Most of the "creative" applications produced by programmers focus on the quantity of the designing possibilities, forgetting that what designers actually need is usually the highest degree of control and an intuitive interface. Good design starts in the mind, not on the computer screen. Spatial operations performed on a two-dimensional screen are particularly challenging. This simple application lets you manipulate the vertices of the spatial BSpline curve of a trefoil knot. On the left is a LocatorPane for manipulating the positions of 15 control points of the knot. At the top right is a perspective view of the knot, and below it are (from left to right) a VerticalSlider for changing the altitude of a selected control point, another VerticalSlider for controlling the thickness of the knot, and a column of three buttons. "Apply " sets the new altitude value for the selected control point, "Flatten" assigns the same vertical coordinate to all the control points, and "Reset" reverts to the initial configuration.