Add a parrable with '+'. Select a parrable by clicking on it; move it with the arrow keys and stretch it with Q&E. Unselect with 'x' and delete with '-'. The red crosses are intercepts with the line and the green crosses are intercepts of two parrables. It looks better with turbowarp: https://turbowarp.org/1273026289?fps=60&hqpen&clones=Infinity&offscreen&limitless
