hello everyone, as a theoretical PhD student I came up (I'm sure I'm not the first ;) ) with an idea. Many times for our work we spend a lot of time just rearranging or making substitutions in quite long equations (I think about the Virasoro algebra in this very moment :D ), something that is just mechanical and tedious, and most of all its RISKY, because we (maybe just me! :) ) end up forgetting on sign or some exponent, wasting hours. At the same time Mathematica is quite fast doing this, but needs a lot of assumptions and many times to type a complicated expression takes so long that its not worth it. But what if we have a tablet pc, or a similar input device. First we could write an equation very quickly, without ctrl+_ and stuff. It would be pretty direct to build up a set of macros relating symbols to mathematica inputs. Then if we want to rearrange terms, we could just select every piece with the pen, drawing a circle or tapping on the bracket around it, and dragging it to a new line. Then we could do a substitution, just by writing down the definition a=b somewhere, selecting it and dragging it on the equation to simplify. To eliminate a term one could just draw a line on it, erasing it on the fly. Mathematica would do just the "mechanical" calculations, so that it would not need lenghty and sometimes ignored assumptions. The notebook would be "clean", being just our input, with the real code "hidden". For sure the usual mathematica input method is way more powerful, but for the "small" purpose of *stupid* calculations this thing can be very helpful. Has anyone an idea on how one could implement this? My programming skills are imaginary :D What else one could do with that? Actually I think that such a thing could speed up my work by 20% at least :D No paper to waste, no cancellations on the sheets, which are annoying and dangerous... I want it!