---
title: "Reset"
description: "What ASW's reset layer does, where it came from, and what it deliberately leaves alone."
type: docs
weight: 60
date: 2026-04-09
tags: ["reset", "css", "reference"]
ai-disclosure: "generated"
ai-model: "claude-sonnet-4-5"
ai-provider: "Anthropic"

---

ASW's reset is in `src/layers/00-reset.css`, ported from [Pico CSS v2.1.1](https://picocss.com/) (MIT). It's an opinionated normalize, not a zero-baseline reset — it corrects browser inconsistencies without stripping all defaults.

---

## What it does

### Box-sizing

Every element uses `border-box`. Padding and border are included in the declared width.

```css
*, *::before, *::after {
  box-sizing: border-box;
  background-repeat: no-repeat;
}
```

`background-repeat: no-repeat` prevents accidental tiling on elements that receive a background image.

### Document baseline

```css
:where(:root) {
  -webkit-tap-highlight-color: transparent;  /* remove tap flash on mobile */
  text-size-adjust: 100%;                    /* prevent font inflation on mobile */
  text-rendering: optimizeLegibility;
  overflow-wrap: break-word;                 /* wrap long URLs / tokens */
  tab-size: 4;
}
```

### Font size

```css
html { font-size: 100%; }
```

Root font size is `100%` of the browser default (typically 16px). Responsive scaling is applied in `01-tokens.css` via `clamp()`. Setting `100%` here respects user accessibility preferences — users who set a larger browser font get a proportionally larger site.

### Body

```css
body {
  width: 100%;
  margin: 0;
  padding: 0;
  font-size: var(--text-base);
  font-family: var(--font-ui);
  background-color: var(--surface);
  color: var(--text);
}
```

All visual values come from ASW tokens. Font and colour are set once here and inherited everywhere.

### Main

```css
main { display: block; }
```

Fixes a legacy IE bug where `<main>` wasn't treated as a block element. Still included for completeness.

### Nested lists

```css
:where(dl, ol, ul) :where(dl, ol, ul) { margin: 0; }
```

Removes the double margin that browsers add to nested lists.

---

## What it leaves alone

The reset deliberately does **not**:

- Zero out heading sizes or margins (those are handled by `02-semantic.css`)
- Remove list styles (lists get `list-style: square` in the semantic layer)
- Reset form element appearance (handled by `03-components.css`)
- Set `line-height` on body (set via `var(--leading)` in `08-layout.css`)

---

## Pseudo-elements

```css
::before, ::after {
  text-decoration: inherit;
  vertical-align: inherit;
}
```

Pseudo-elements inherit text decoration and vertical alignment from their parent. This prevents `::before`/`::after` content from appearing unexpectedly underlined in links.

---

## Customising the reset

The reset layer uses low-specificity `:where()` selectors where possible. Override anything with a standard selector — no `!important` needed.

```css
/* Override: use rem-based font scaling instead of responsive clamp */
html { font-size: 1rem; }

/* Override: add body padding for a specific layout */
body { padding-inline: var(--space-4); }
```

---

## Related

- [Semantic HTML](/docs/semantic-html/) — element styles built on top of this reset
- [Token System](/docs/tokens/) — the custom properties (`--surface`, `--text`, `--font-ui`) referenced in this layer