Aspects
Skills
Skills are numerical attributes that represent your character’s proficiency and level of training in a particular field or at a particular set of tasks.
Leveling skills
Your character starts with a 0 in each skill. To increase your level in a skill by one, you must pay XP equal to the skill’s new level. For example, to increase a skill to level 10 from scratch, you have to pay a total of 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55 XP. Some skills are “double-cost” or “half-cost”, meaning that you pay double or half that amount.
The total cost to buy a skill all the way up to level N is N * (N+1) / 2.
The skill pyramid
In order for a skill list to be valid, the number of your skills with aspect bonus N cannot exceed the number of your skills with aspect bonus N-1. If you are spending large amounts of XP at once, you can jump directly to another valid state. You are assumed to have an arbitrary number of skills at level 0.
This rule, along with the increasing cost to level the same skill, is meant to encourage branching out and having multiple skills relevant to your character, leading to more varied gameplay.
Half-cost Discount
Some groups of related skills have a half-cost discount. This means that, when purchasing a level of a skill in the group, if the old level is less than the highest skill level in the group, you pay only half the XP. Fractional XP is accounted for; you do not have to round up or down.