I think spark is not very realistic and can be easily duplicated, so i suggest Electricity. In real life, electricity is the movement of electrons. And this movement is because of voltage between two conductors. My idea is that tmp2 or something should be used to hold the amount of charge a particle has. When any particle touchs another that has a different tmp2 they should conduct. But every conductor should be different, some should conduct fast and some should conduct slow. With that added to the game making reactors would make more sense because you can make infinite amount of spark and that is not really logical. I did not think of everything but i think there can be stuff like RSTR(resistor), CPCT(capacitor), LEDL(led), DIOD(diode). But to add these we would also need something like PSDE and NSDE which will be connected to the sides of particles like these. For example capacitor can use tmp2 for something else, it can be how much charged it is and unlike normal electricity it can only conduct to PSDE and NSDE in a different way. When there is a voltage between PSDE and NSDE then it can charge. Also when ELEC hits a conductor, it can charge it.
If SPRK was replaced with the suggested "electricity", that would break tons of saves, so no support. Maybe someone could make it a mod tho.
What if it was a new element? Any way good idea but there is really no use for it now, electronics as ready complicated. BUT each conductor TMP (or TMP2 if tmp is being used for something) determines its "resistance" This determines the amount of spaces spark would jump. The normal value is TMP(2): 1. The spark will jump one space as usual. Spark will stay the same, but electrons will be generated in a sphere (tmp+tmp by tmp(my math may be wrong :( )) So other saves won't break, this doesn't add anything new, just make something that already happens more visible.
Ok, maybe that could work. Maybe.
Here's my idea: tmp1 and tmp2 will be SPRK speed, just like vx and vy, sparks are like photons confined to an area.
When 2 SPRKs collide, their tmp1 and tmp2 get combined And A single spark continues on with the sums of the collision.