We present examples of student work from the course Golden Ratio at Eindhoven University of Technology (TU/e) where students learn about tessellations, fractals, splines and Processing. One of the difficulties in designing new tessellations is how to find a basic figure which is attractive or has a meaning and which satisfies the formal requirements of fitting in a complex tiling. In earlier work we combined turtle graphics and splines, which turned out useful for certain projects, yet did not complete solve the problem of how to make the difficult creative step. This year several students created their own interactive mini-tools for designing a type of tessellation of their own choice. The following strategy was found effective: choose a type of tessellation, typically a Heesch-Kienzle type, perhaps with an extra twist, and then build a mini-tool in Processing where the edges of the basic figure can be manipulated interactively using one of the variations of spline theory. We present coding details and examples.