It is a little difficult to tell, but it seems that the gas "atoms" all have the same speed rather than a Boltzmann distribution. This simulation should be presented as a qualitative model.
The scale on the pressure gauge has no units.
The terms momentum, speed and kinetic energy are used interchangeably by the
author (as being dependent on changes of T). This could be a bit confusing to
the beginning user. The meaning of the constant of proportionality (between P
and T) is not addressed.