Pokédex: How It Works
A Pokédex is a structured database of a few thousand creatures with typed relationships, base statistics and evolution chains. It is also an unusually clear example of a well-designed type system, which is why the underlying maths is worth understanding.
The type chart is the game
Eighteen types interact through a matrix of multipliers, and understanding it is most of competitive play.
| Matchup | Damage multiplier |
|---|---|
| Super effective | ×2 |
| Neutral | ×1 |
| Not very effective | ×0.5 |
| No effect | ×0 |
Multipliers stack across a dual-typed target, so a move can be ×4 or ×0.25. A Water move against a Rock/Ground creature hits for ×4, because it is super effective against both types. This is why dual typing is a trade — it grants resistances and creates a much larger weakness.
The immunities are worth memorising because they are absolute: Normal does nothing to Ghost, Electric nothing to Ground, Poison nothing to Steel, Dragon nothing to Fairy, Ghost nothing to Normal, and Psychic nothing to Dark.
Base stats and what they mean
| Stat | Governs |
|---|---|
| HP | Damage that can be absorbed |
| Attack / Special Attack | Damage dealt by physical / special moves |
| Defense / Special Defense | Damage taken from each category |
| Speed | Move order — often decisive |
Base Stat Total is a rough measure of overall power and a poor measure of usefulness. A creature with a high total spread evenly across all six stats is frequently worse than one with a lower total concentrated where it matters, because a battle rewards excelling at one job rather than being adequate at all of them.
Speed is the stat that most changes outcomes, since moving first often decides an exchange outright.
Evolution
Evolution methods go well beyond levelling: elemental stones, trading, high friendship, time of day, held items, location, learned moves, and in some cases conditions obscure enough that they were discovered by data mining rather than play. A database is genuinely necessary for these — several are not discoverable in normal play.
Reading a Pokédex entry critically
The flavour text is written for tone rather than consistency, and entries across games frequently contradict one another. Listed heights and weights produce absurdities when compared, and some entries describe capabilities the creature does not have in the games. It is worldbuilding, not specification, and reading it as canon leads to arguments that cannot be settled.
Why the design has lasted
A type chart with eighteen elements has 324 relationships, and it is close to balanced — every type has answers, no type dominates, and adding Fairy in a later generation was a deliberate correction to Dragon's dominance. That a system this large stays balanced while remaining learnable is a genuine design achievement, and it is the reason the underlying strategy has held up across three decades.