CSS Reset

My opinionated CSS reset for new projects.

@layer reset {
  *, *::before, *::after { transition: all ease-out 100ms; margin:0; padding: 0; box-sizing: border-box; vertical-align: baseline; min-width: 0; scroll-behavior: smooth }
  :where(html) { text-size-adjust: none; -webkit-text-size-adjust: none; -moz-text-size-adjust: none; --bodyFontSize: clamp(13.5px, 2.4vw, 16px); --bodyFontColor: #323232; tab-size: 4; font-family: 'Work Sans', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif ; color: var(--bodyFontColor); line-height: 1.5; -webkit-font-smoothing: antialiased; font-size: var(--bodyFontSize); }
  :where(:not(:defined)) { display: block; }
  :where(:is(body, html)) { width: 100%; height: 100%; }
  :where(:is(img, picture, video, canvas, svg)) { display: block; max-width: 100%; vertical-align: middle; }
  :where(:is(input, button, textarea, select):not([disabled])) { font: inherit; cursor: pointer; }
  :where(*:not(:is(main, body, .prose, .app, .root, #root)) > :is(h1, h2, h3, h4, h5, h6)), :where(p) { font-size: inherit; font-weight: inherit; overflow-wrap: break-word; text-overflow: ellipsis; background-color: inherit; }
  :where(:is(h1, h2, h3, h4, h5, h6)) { text-wrap: balance; letter-spacing: 0.2px; scroll-padding-block: 1lh; }
  :where(p) { text-wrap: pretty; }
  :where(textarea) { form-sizing: content; min-height: 2lh; max-height: 10lh; }
  :where(button) { box-sizing: content-box; text-box-trim: both; text-box-edge: cap alphabetic; }
  :where(:is(#root, #__next, div#app)) { isolation: isolate; }
  :where(table) { text-indent: 0; border-color: inherit; border-collapse: collapse; border-spacing: 0; }
  :where(*:not(p) ~ :is(ul, ol) > li), .list-style-none { list-style: none; }
  :where([src='']) { visibility: hidden; }
  *::backdrop { all:unset; }
  :where(modal::dialog) { max-width: 100dvw; max-height:100dvh; }
  :where(:not(:is(html, audio, textarea, body, main, table, button, checkbox, input, td, tr, th, tbody, table, tfoot, video, form, details, select, summary, fieldset, hr, *::before, *::after, frame, iframe, datalist, object))) { border-style: solid; border-width: 0; }
  :where(:is(a:empty, ul:empty, dl:empty, div:empty, section:empty, article:empty, p:empty, h1:empty, h2:empty, h3:empty, h4:empty, h5:empty, h6:empty)) { display: none; }
  :where(.display-none) { display: none; }
  :where(:target) { scroll-margin-block: 5ex; }
  @media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; transition: none; animation-name: none; } }
  @view-transition { navigation: auto; }
}

With comments

/* Everything is in the reset layer so it can be easily overwritten. */
@layer reset {
  /* Applies to everything */
  *, *::before, *::after { 
    /* I think having some sort of transition is usually the behaviour I want. */
    transition: all ease-out 100ms; 
    /* Controversial, but I like having a clean slate of margin / padding. */
    margin:0; 
    padding: 0; 
    /* Resets to what I believe most people already assume is the case. */
    box-sizing: border-box; 
    vertical-align: baseline;
    min-width: 0;
    scroll-behavior: smooth;
  }

  /* Everything is defined with :where so they have zero specificity and can easily be overwritten. */
  
  :where(html) { 
    /* Fixes safari zoom issue */
    text-size-adjust: none; 
    -webkit-text-size-adjust: none; 
    -moz-text-size-adjust: none; 

    /* My preferred text settings. */
    --bodyFontSize: clamp(13.5px, 2.4vw, 16px);
    --bodyFontColor: #323232;
    tab-size: 4; 
    font-family: 'Work Sans', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif ; 
    color: var(--bodyFontColor);
    line-height: 1.5; 
    -webkit-font-smoothing: antialiased; 
    font-size: var(--bodyFontSize);
  }

  /* Makes webcomponents / unknown elements display as you'd expect */
  :where(:not(:defined)) { 
      display: block; 
  }

  /* What most would already expect the size of the width / height to be. */
  :where(:is(body, html)) { 
    width: 100%; 
    height: 100%; 
  }

  /* Fixes common media element issues */
  :where(:is(img, picture, video, canvas, svg)) { 
    display: block; 
    max-width: 100%; 
    vertical-align: middle; 
  }

  /* Makes the font / cursor of inputs what you'd probably expect. */
  :where(:is(input, button, textarea, select):not([disabled])) { 
    font: inherit; 
    cursor: pointer; 
  }

  /* Headings / text outside of the normal places should look like normal text  */
  :where(*:not(:is(main, body, .prose, .app, .root, #root)) > :is(h1, h2, h3, h4, h5, h6)), :where(p) { 
    font-size: inherit; 
    font-weight: inherit; 
    overflow-wrap: break-word;
    text-overflow: ellipsis;
    background-color: inherit;
  }

  /* Normal headings should look like / act headings */
  :where(:is(h1, h2, h3, h4, h5, h6)) { 
    text-wrap: balance; 
    letter-spacing: 0.2px; 
    scroll-padding-block: 1lh; 
  }

  /* Make text pretty */
  :where(p) { 
    text-wrap: pretty
  }

  /* Auto-grow text areas. */
  :where(textarea) { 
    form-sizing: content; 
    min-height: 2lh; 
    max-height: 10lh; 
  }

  /* Allow button borders to escape their containers. I think this is what most people want. Also, trim additional space in buttons */
  :where(button) { 
    box-sizing: content-box;
    text-box-trim: both;
    text-box-edge: cap alphabetic;
  }

  /* SPA containers should be isolated. Maybe will help with css performance? Doubt it tho. */
  :where(:is(#root, #__next, div#app)) { 
    isolation: isolate; 
  }

  /* Tables as you probably want them. */
  :where(table) { 
    text-indent: 0; 
    border-color: inherit; 
    border-collapse: collapse; 
    border-spacing: 0; 
  }

  /* Lists that arnt next to text should not have bullet points. */
  :where(*:not(p) ~ :is(ul, ol) > li), .list-style-none { 
    list-style: none; 
  }

  /* Hide blank images  */
  :where([src='']) { 
    visibility: hidden; 
  }

  /* Fixes unexpected popover backdrop issues */
  *::backdrop { 
    all:unset;
    position: fixed;
    inset: 0;
    opacity: 0.7;
  }

  :where(modal::dialog) { 
    max-width: 100dvw; 
    max-height:100dvh; 
  }

  /* Makes so if just a border color / width is defined, then it'll still work as expected */
  :where(:not(:is(html, audio, textarea, body, main, table, button, checkbox, input, td, tr, th, tbody, table, tfoot, video, form, details, select, summary, fieldset, hr, *::before, *::after, frame, iframe, datalist, object))) { 
    border-style: solid; 
    border-width: 0; 
  }

  /* Hides empty elements */
  :where(:is(a:empty, ul:empty, dl:empty, div:empty, section:empty, article:empty, p:empty, h1:empty, h2:empty, h3:empty, h4:empty, h5:empty, h6:empty)) { 
    display: none; 
  }

  /* Everyone will probably need this at some point */
  :where(.display-none) { 
    display: none; 
  }

  :where([hidden], .visually-hidden) {
    clip: rect(0 0 0 0); 
    clip-path: inset(50%);
    height: 1px;
    overflow: hidden;
    position: absolute;
    white-space: nowrap; 
    width: 1px;
    content-visibility: hidden;
  }

  /* Makes Url heading targets display in view. */
  :where(:target) { 
    scroll-margin-block: 5ex; 
  }

  /* Simple prefers reduced motion compliance */
  @media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { 
      animation-duration: 0.01ms !important; 
      animation-iteration-count: 1 !important; 
      transition-duration: 0.01ms !important; 
      transition: none; 
      animation-name: none; 
    } 
  }

  /* Turns on view transitions */
  @view-transition { 
    navigation: auto; 
  }
}