Unisim

Particle Simulator

Application to simulate particles and their interactions

Also, simulates collisions between particles in a continuous way

Includes gravity, electrical forces and an invented weak force 

Check out the project on GitHub

You an set up the different constants of particles in the add menu

You can open the menu with Escape, and everything is explained in the Help menu.

You can additionaly find a changelog in the Info menu.

The Control menu, found in the second page of the Options menu, lets you change most keybinds.

Screenshots are saved in [APPDATA]/ashproject/unisim/screenshots

Saved files are usually saved in  [APPDATA]/ashproject/unisim/saves, although you can change it in the options