The first two games were accidently played with an experimental armour system, whereby GA is 50, YA 100 and RA 150 - however armor stacks, up to (armorvalue + 50), eg:
If you have 0 armour and walk over YA, you get 100a.
If you have 25 armour and walk over YA, you end up with 125a.
If you have 50 armour and walk over YA, you end up with 150a.
And if you have 75 armour and walk over YA, you end up with 150a (because 100 + 75 > 150, ie: armour value + 50).