Pressure is nothing but molecules hitting the wall. Each collision delivers a small push, and the pushes are added up over time and divided by the wall length. That is the measured pressure. The theoretical value comes from PV ＝ NkT with the same temperature, volume, and count.
Raise the temperature and the molecules speed up. Pull the piston in and the same molecules hit a shorter wall more often. Add molecules and there are simply more collisions. All three raise the pressure, and the measured bar keeps up with the theoretical one every time.
The colour of a molecule is its speed, blue for slow and red for fast. At any temperature both are present, because the speeds are spread out rather than shared equally.
The distribution panel counts the molecules by speed and lays the theory over the bars. Since the stage is two-dimensional, the curve is the two-dimensional Maxwell distribution, f(v) ＝ (v ／ σ²) exp(−v² ／ 2σ²), whose peak sits at v ＝ σ. Raise the temperature and the whole hill slides right and flattens: the fast tail grows, but no single speed is ever shared by everyone.
The panel names at the top right open and close each panel. Drag a panel by its header to move it: panels snap to each other and to the screen edge, and a panel resting on an edge drops the rounded corner on that side. Double-click a panel title to switch between floating panels and a single fixed panel at the top right. Pick a row in the condition panel and its value appears in the child panel beside it, which follows the parent as it moves.