Random 2D curve generator

I need a software module (with simple GUI that demonstrates its abilities) that generates random 2D curves (Bezier or cubic splines) to form a continuos curve that could be used as an object path in a computer game. See examples attached. More good examples - game paths in puzzle games such as Zuma, Luxor, Sparkle etc. Requirements: - low error rate (80-90% of generated curves should be OK - must have no wrong intersections, segments too close to each other, etc.) - have some parameters (demonstarted in GUI too) to control the style of the curves (more circular levels, or levels with more straight lines (sample 3,4)) quantity of spiral or repeating patterns (sample 1,2,5,6) - must be able to generate 1 or 2 curves (when used in 2 curves mode there should also a low error rate (60+% of good curves) - should be written on C++ or C# - source code provided (when job accepted) - good quality code with comments and modularity (will be integrated in our project)