# Scales

HTML: [altophp.com/scale/scales](https://altophp.com/scale/scales/)

Choose the progression according to the relationship between consecutive
values.

| Scale | Relationship | Typical use |
| --- | --- | --- |
| [Modular](scales/modular.md) | Multiply by one ratio | Type sizes, proportional spacing |
| [Linear](scales/linear.md) | Add one increment | Baseline grids, fixed spacing |
| [Fibonacci](scales/fibonacci.md) | Follow Fibonacci numbers | Integer rhythms and counts |
| [Multi-strand](scales/multi-strand.md) | Interleave several modular scales | Multiple coordinated bases |

Every type implements `ScaleInterface`, so application code can accept any
scale while using `get()`, `stepOf()`, `snap()`, and `range()`.

```php
use Alto\Scale\ScaleInterface;

function tokens(ScaleInterface $scale): array
{
    return $scale->range(-2, 5);
}
```

The shared contract does not imply identical domains. Modular and multi-strand
scales require positive values for logarithmic lookup. Linear scales can cross
zero. Fibonacci lookup maps non-positive values to step zero.

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Previous: [Getting started](https://altophp.com/scale/getting-started.md)
Next: [Modular scales](https://altophp.com/scale/scales/modular.md)

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ALTO\SCALE: [altophp.com/scale](https://altophp.com/scale/)
ALTO(PHP): [altophp.com](https://altophp.com/)