An ideal gas simulator that I whipped up in FORTRAN in a few days as my first big project in the language. Simulates a 2D box of ideally behaving particles, and calculates the pressure based off of the mean force on the box. As far as I can tell, it gets the pressure about 60-80% right. Not sure where to improve the code in order to improve simulation results. I'm unsure if the simulation is off due to the fact that it is only 2D.
Go to the I/O folder, and open input.txt. Here, you can change the simulation conditions freely before you begin. Once done, just run sim.exe to start! The results will populate into output.txt.