Compare the lifebuoy spawn chance with the original

[ForNeVeR]

Currently, about 20% of all bonuses will become lifebouys. We should compare this with the original game.

See the code near this line:

O21/O21.Game/Engine/GameRules.fs

Line 152 in 75e0801

let LifebuoySpawnChance = 0.2 // TODO: Compare with the original