Captain Anorak's Guide to Gaming
Game Mechanics: Task Resolution
One of the most basic parts of a game mechanics system is how it resolves tasks. That is, a character tries to do something, and game mechanics have a system to determine whether he succeeds or fails (and, in some games, how well he succeeds or fails).

The simplest task resolution system is to have a skill level, and to make a simple roll-under test against it. Basic Roleplaying, the rules system used for Call of Cthulhu and RuneQuest, uses percentile skills like this, so if a character has a 40% skill then he succeeds on a D100 roll of 40 or less. A modifier to the skill might be made if task is particularly easy or difficult.

This frequently fails to represent reality. To illustrate this, let me use the example of something I know about in real life: climbing. Im am an experienced climber with a middle level of ability: I'm not a world-class climber but I'm a lot better than a beginner. When I go climbing, I only ever attempt climbs where I believe that there is no risk to me - that is, my assessment is that my chance of success is 100%. Most sensible climbers behave the same way. There are some climbers who do take risks, but they tend to have accidents and get killed or crippled, so they don't survive to become experienced climbers. Consequently, a lot of highly experienced climbers have never had an accident.

This doesn't mean that experienced climbers only attempt easy climbs. I have climbed things which other people with me considered impossible, but which I regarded as entirely within my ability. I would rate such climbs as being in the mid-level of dificulty: challenging for a reasonably skilled climber (but still safely within ability), but easy for a highly experienced climber.

Realistically, the chances of success should be like this:
- A complete beginner should be able to make really easy climbs with no chance of failure, but should risk failure with anything else.
- A reasonably experienced climber should be able to make middle-level climbs with no chance of failure, but should risk failure with difficult climbs.
- A highly experienced climber should be able to make fairly climbs with no chance of failure, and should risk failure only with with extremely difficult climbs.

This could never happen in Call of Cthulhu. In CoC, a beginner has Climb skill 40%. Presumably a middle-level climber like me would have something like Climb 65% and a really experienced climber would have around Climb 90%. The rules (5th Edn, page 39) call for a roll (presumably unmodified) every 10-30 feet of climbing, depending on difficulty. It is implied that failure results in falling.

This means that a highly experienced climber (skill 90%) climbing an easy slope (1 roll per 30 feet) of 210 feet (64 metres) must make 7 Climb rolls. One failure would result in falling. This makes his chance of passing all his Climb rolls just under 48% - he is more likely than not to fall from climbing a mere 64m of easy slope. This is utterly ludicrous! In reality, a mid-level climber like me can climb 64m of easy slope zero risk of falling; a highly experienced climber can climb hundreds of metres of easy slope in a day with no risk.

In CoC it is impossible for any character to become an experienced climber, because a beginner (skill 40%) will usually fall on every 30 feet of easy climbing, taking 1D6 Hit Points per 10 feet fallen (an average character has 12 HP). Within a few practise climbing sessions, an injury would kill any character before he gained enough experience to reach a high Climb skill level.