The skill leveling system seems to be based on percentages, and each level seems to be 1% increase. (Ex. my Speed Up skill is level 18, but the difference only seems to be a noticeable, but only slight increase in how fast the loop moves.) The stat levels seem to be less linear and more like a x+((x*y)/z), with x being base speed (that being one, but I am not sure if this is increased by skill values), y being the total level increase (the right stat value), and z being the level that has been increased in the run (the left stat value). (Ex. speed level being 50(y), run level being 20(z), and base being 1(x), so the equation ends up being 1+((50*1)/20)=2.5% increase per activity tick. Some activities have multiple checks, such as running on the treadmill in this case.) Also, some values will temporarily stay after being manipulated in the previous run until you make an action that causes it to be checked.
Anyway, the game is fun, but it could use a proper save system, a skill x stat x mult. interaction system implementation, and item usage system.