1. Dwelling: Income = BaseIncome; Increase = BaseIncrease * (1 + FortressBonus)
2. Upgrade: Income = BaseIncrease * (1 + FortressBonus)
3. FortressBonus:
Fortress = +100% for tiers 1-2
Citadel = +100% for tiers 1-4
Castle = +100% for tiers 1-6
Is this a simple enough scheme to understand?
In other words, FortressBonus = [FortressLevel - (Tier-1)/2] or 0. This formula is interesting because, if rounding is removed, it can produce not 3, but all 6 gradations of bonuses for different tiers:
Fortress = +100% for tier 1, +50% for tier 2
Citadel = +100% for tiers 1-3, +50% for tier 4
Castle = +100% for tiers 1-5, +50% for tier 6
But this is a more complex option. Is it worthwhile?