The graph-dragging interface is very difficult for me to use on mobile (Firefox on Android; most of the times I tried to grab a point to move it up or down, it just added a new point between two existing ones and moved that instead. I definitely can understand that it's hard to make an interface to allow a user to draw an arbitrary curve, but I feel like this could be solved by just limiting the granularity of the points the user can select further; I really don't feel like the experience is improved by being able to select eight or so different points that all have to fit horizontally on the right half of my phone screen.