CLAMPING
XP clamping is when the game slows down XP gain in an act after a hero levels up. It prevents a hero from leveling up too quickly, and keeps level ups consistent across runs and acts. Once a hero's level passes the act number, clamping reduces XP gain by 90%. This makes options which gain more XP less valuable. Understand that the only benefit clamping can give us is through time spent. We cannot gain more experience than we otherwise could through any methods.
An example. At velka_17 we have the forge entry with 4 choices.
[Leave] Gives us no XP, and does not enter the forge so we will not do this.
[Enter] Each character that succeeds will receive 32 XP. There is no way to critically Succeed this choice.
[Open] Upon success each character receives 40 XP. On a crit, this number will be 44 instead.
[Nenukil’s unique interaction] or [Wilbur’s unique interaction] Each character will receive 32 XP. There is no way to critically Succeed this choice.
If we instead assume we are past the clamp point, all of these XP numbers will be divided and rounded, therefore:
[Enter] 3.2 rounded down to 3XP each.
[Open] 4 XP each
[Open] Crit 4.2 rounded down to 4XP each
[Character interactions] 3.2 rounded down to 3XP each.
Therefore we know that [Open] is the correct choice, and if we are past the clamp point, a success is worth as much to us as a critical.
This seems simple enough, but when accounting for multiple acts, things get crunchy.
Suppose each level up requires 300 XP and we gain exactly that each act. The 300 XP will go to leveling as per normal, and there is no extra XP that gets clamped, so the act XP chart will look like so.
A1 End: 300 XP
A2 End: 600 XP
A3 End: 900 XP
A4 End: 1200 XP
Now suppose we add another 1000 XP to act 4. Because we would have reached the clamp point, the end of A4 XP would be 1200 + (1000/10)
A4 End: 1300XP
Now let’s add the 1000 XP to act 1 instead. Because we reach the clamp point and go past the expected XP gain for the act, it will make the next act reach the clamp point faster like so…
A1 End: 300 + (1000/10)
= 400 XP
As amount of XP needed to get to the clamp point in A2 is unchanged, and we only need to get 200 XP to get to the A2 clamp point, the A2 calculation looks like this.
A2 End: 400 + 200 + (100/10)
= 610 XP
A3 End: 610 + 290 + (10/10)
= 901 XP
A4 End: 901 + 299 + (1/10)
= 1200.1 (will be rounded down to no gain)
With this example we can see that for each act we go through, the XP gained from the previous act is divided. For this reason, we care a lot less about XP optimisation in the earlier acts than in the later acts.