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CSS Design Notes

CSS Framework Key Points​

  • Design tokens.
  • Content.
  • Centering.
  • Spacing.
  • Color and contrast.
  • Balance (position).
  • Primary and secondary color.
  • Custom text (font).
  • Font family.
  • Images and links.

Typography Principles​

  • The typeface (font-family).
  • Type (modular) scale.
  • Responsiveness of the text (size unit and breakpoints).
  • Spacing and vertical rhythm.
  • Colors (theming).

Refer to: font-family, font-size, spacing, color.

Typography Properties​

Typography Properties

Font Size​

  • Set a base-size.
  • Multiples of base-size.
  • Use rem for most font-size, use em for some spacing (needing responsive design).
  • rem is better.
  • em for responsive layout: e.g layer2 font based-on layer1 font in dropdown menu.
  • Make text legible: at least 16px.
$xs: $base / $ratio / $ratio;
$sm: $base / $ratio;
$md: $base;
$lg: $base * $ratio;
$xl: $base * $ratio * ratio;

Font Typeface​

Prefer web fonts:

  • Especially in headings, because of consistency.
  • Keep it to 2 to 5 font files or below 100 kb.
  • Use system fonts for body text or UI text, if you have to.

Spacing​

Make text breathe:

  • margin/padding: at least 15px.
  • line-height: 1.4.
  • word-spacing.
  • letter-spacing.
  • 60-100 characters per line.

Vertical Rhythms​

Keep vertical spaces between elements on a page consistent (and relative) to each other:

  • Set the vertical white space between elements to a multiple of base-size.
  • Set the line-height of all text elements to a multiple of base-size.
  • Set margin-top and margin-bottom to <h1> ~ <h6>/<hr> elements set margin-bottom to normal elements.

Line Length​

The optimal line length for body text is 50–75 characters:

  • Shorter or longer line lengths can hurt readability.
.line-length {
  margin-top: 2em;
  line-height: 1.5em;
  letter-spacing: 0.12em;
  word-spacing: 0.16em;
}

Table Typography​

  • Remove fills, grid lines, border and bolding.
  • Left-align text, right-align numbers and align headings with data.
  • Put white space to work to group and separate.

Typography Reference​

Responsive Design​

Responsive web design:

  • Mobile first: @media only screen and (min-width: 768px).
  • Media query.
  • Fluid layout.
  • Flexible image.

Mobile Viewport​

Disable mobile browser auto scale:

<meta name="viewport" content="width=device-width, initial-scale=1" />

Responsive Font​

  • rem/em font size.

Responsive Length​

  • vw.
  • vh.
  • vmin: min(vw, vh).
  • vmax: max(vw, vh).

Responsive Size​

Responsive font size;

  • Size in em if the property scales according to it's font-size: e.g button padding.
  • Modular font size: Size in em if the font-size should be modular (relative to it's context/parent).
  • Size everything else in rem (include @media queries).
/* scales to self font-size */
.container {
  margin-top: 1.2em;
}
/* modular font size */
.container {
  font-size: 1.2rem;
}

.container p {
  font-size: 1em;
}

.container small {
  font-size: 0.9em;
}

Responsive Box​

Responsive Width and Height​

  • min-height.
  • max-height.
  • min-width.
  • max-width.
/* responsive images */
img {
  display: block;
  max-width: 100%;
}
Image Display

Image display set to inline default.

Responsive Inline Box​

use inline-box with width

.element {
  display: inline-box;
  width: 80%;
}

Responsive Flex Box​

.box {
  display: flex;
  flex-wrap: wrap;
}

.box > .item {
  flex: 1;
}

Responsive Grid Box​

.box {
  display: grid;
  grid-template-areas:
    'hd'
    'st1'
    '.'
    'st2'
    '.';
  grid-template-columns: 1fr;
}

@media only screen and (width >= 768px) {
  .box {
    grid-template-areas:
      'hd hd'
      'st1 .'
      '. st2';
    grid-template-columns: 1fr 1fr;
  }
}

@media only screen and (width >= 1280px) {
  .box {
    grid-template-areas:
      'hd hd hd'
      'st1 . st2'
      'st1 . st2';
    grid-template-columns: 1fr 1fr 1fr;
  }
}

@media only screen and (width >= 1536px) {
  .box {
    grid-template-areas:
      'hd st1 . st2'
      'hd st1 . st2';
    grid-template-columns: 20% 1fr 1fr 1fr;
  }
}

Responsive Image​

.responsive-image {
  display: block;
  max-width: 100%;
  height: auto;
}
<picture>
  <source srcset="mdn-logo-wide.png" media="(min-width: 600px)" />
  <img src="mdn-logo-narrow.png" alt="MDN" />
</picture>

<img
  src="x-small.png"
  srcset="x-small.png 300w, small.png 400w, medium.png 600w, large.png 800w, x-large.png 1200w"
  sizes="
    (min-width: 70em) 12.6875em,
    (min-width: 50em) calc(25vw * 0.95 - 2.75em),
    (min-width: 35em) calc(95vw / 2 - 4.125em),
    calc(95vw - 1.375em)
  "
  alt="Dummy Image"
/>

Responsive Table​

table {
  width: 100%;
}

@media (width <= 30em) {
  table,
  thead,
  tbody,
  tr,
  th,
  td {
    display: block;
  }

  tr {
    margin-bottom: 1em;
  }

  /* 隐藏表头 */
  thead tr {
    position: absolute;
    top: -9999px;
    left: -9999px;
  }
}

Design Systems​

Design Tokens​

Design tokens are the atomic building blocks of a design system. Think of them as named containers that store your website’s visual DNA:

  • Colors.
  • Fonts.
  • Spacing.
  • Sizing
  • And more.

Design Tokens Importance​

  • Consistency: A token like “brand-blue” with the value “#006699” ensures that exact blue is used everywhere. This extends to spacing, typography, and more.
  • Maintainability: Update the token, and changes ripple through your entire application to complete a design refresh.
  • Scalability: Design tokens keep your growing projects organized. New components inherit your design rules, guaranteeing a unified look.
  • Collaboration: Tokens become a shared language between designers and developers, a single source of truth for your website’s style.

Design Tokens Implementation​

Tiered structure: we define tokens at different levels of abstraction:

  • Tier 1: Base value (--color-brand-blue-800).
  • Tier 2: Semantic meaning (--theme-color-content-default).
  • Tier 3: Component-specific use (--theme-color-button-content).
<script>
  // my-button.js
  class MyButton extends HTMLElement {
    // ... your component setup

    connectedCallback() {
      this.shadowRoot.innerHTML = `
       <style>
         button {
           background-color: var(--theme-color-button-content); /* Tier 3 token */
           padding: var(--spacing-base);
           color: var(--theme-color-content-default);
         }
       </style>
       <button><slot>Default Button</slot></button>
     `
    }
    // ... rest of your component code
  }

  customElements.define('my-button', MyButton)
</script>

<style>
  /* Design tokens as CSS custom properties */
  :root {
    --color-brand-blue-800: #069; /* Tier 1 */
    --theme-color-content-default: var(--color-brand-blue-800); /* Tier 2 */
    --theme-color-button-content: var(--theme-color-content-default); /* Tier 3 */
  }
</style>

Implementing design tokens in your workflow:

  • Design Phase: Defining Visual DNA:
    • Define your design tokens in a shared document.
    • Use tools like Figma, Sketch, or Adobe XD to create a design system.
    • Craft the core visual attributes: color palettes, typography, spacing and sizing.
    • Define tokens hierarchical structure: this is where tokens become powerful.
  • Exporting Phase: Generating Tokens:
    • Use tools like Token Studio, Style Dictionary, or Figma Tokens to generate tokens.
    • Export tokens in a format (JSON/YAML) that can be consumed by your development environment.
    • Define a naming convention for your tokens.
    • Take use of version control and continuous integration.
  • Development Phase: Implementing Tokens:
    • Create a CSS file to store your tokens.
    • Use CSS custom properties to define your tokens.
    • Implement tokens in your components.
    • Component library integration: include the generated styles in your component library environment setup (e.g Storybook).
  • Maintenance Phase: Updating Tokens:
    • Regenerate tokens and update your CSS file: design systems aren’t static.
    • Test your components to ensure the changes are applied correctly.
    • Use version control to track changes.

CSS Design Tokens​

Theming with modern CSS:

:root {
  /* Fluid type scale core tokens */
  --size-step-minus-2: clamp(0.6944rem, 0.6376rem + 0.284vi, 0.84rem);
  --size-step-minus-1: clamp(0.8333rem, 0.7488rem + 0.4228vi, 1.05rem);
  --size-step-0: clamp(1rem, 0.878rem + 0.6098vi, 1.3125rem);
  --size-step-1: clamp(1.2rem, 1.028rem + 0.8598vi, 1.6406rem);
  --size-step-2: clamp(1.44rem, 1.2016rem + 1.1918vi, 2.0508rem);
  --size-step-3: clamp(1.728rem, 1.402rem + 1.6302vi, 2.5635rem);
  --size-step-4: clamp(2.0736rem, 1.6323rem + 2.2063vi, 3.2043rem);
  --size-step-5: clamp(2.4883rem, 1.8963rem + 2.9602vi, 4.0054rem);
  --size-step-6: clamp(2.986rem, 2.1974rem + 3.943vi, 5.0068rem);
  --size-step-7: clamp(3.5832rem, 2.5392rem + 5.2201vi, 6.2585rem);

  /* Fluid space scale core tokens */
  --space-3xs: clamp(0.25rem, 0.2256rem + 0.122vi, 0.3125rem);
  --space-2xs: clamp(0.5rem, 0.4268rem + 0.3659vi, 0.6875rem);
  --space-xs: clamp(0.75rem, 0.6524rem + 0.4878vi, 1rem);
  --space-s: clamp(1rem, 0.878rem + 0.6098vi, 1.3125rem);
  --space-m: clamp(1.5rem, 1.3049rem + 0.9756vi, 2rem);
  --space-l: clamp(2rem, 1.7561rem + 1.2195vi, 2.625rem);
  --space-xl: clamp(3rem, 2.6341rem + 1.8293vi, 3.9375rem);
  --space-2xl: clamp(4rem, 3.5122rem + 2.439vi, 5.25rem);
  --space-3xl: clamp(6rem, 5.2683rem + 3.6585vi, 7.875rem);

  /* Colors core tokens */
  --color-light: #fff;
  --color-light-shade: #f3f5f7;
  --color-dark: #000;
  --color-mid: #ebebeb;
  --color-mid-shade: #dedede;
  --color-midnight: #4a4e69;
  --color-midnight-shade: #22223b;
  --color-eggshell: #f2e9e4;
  --color-blue: #3b71fe;
  --color-blue-glare: #eef6fd;
  --color-slate: #4f5563;

  /* Abstract into more specific, semantic variables */
  --leading: 1.5;
  --leading-short: 1.3;
  --leading-fine: 1.1;
  --leading-flat: 1;
  --leading-loose: 1.7;
  --kerning: normal;
  --kerning-tight: -0.04ch;
  --kerning-loose: 0.1ch;
  --text-size-base: var(--size-step-0);
  --text-size-meta: var(--size-step-minus-1);
  --text-size-heading-1: var(--size-step-5);
  --text-size-heading-2: var(--size-step-4);
  --text-size-heading-3: var(--size-step-3);
  --text-size-heading-4: var(--size-step-2);
  --text-size-prose: var(--text-size-base);
  --space-gutter: var(--space-m);
  --space-gutter-s: var(--space-s);
  --space-gutter-l: var(--space-l);
  --space-regions: var(--space-xl);
  --size-wrapper-max-width: 1135px;
  --color-global-bg: var(--color-light);
  --color-global-text: var(--color-dark);
  --color-surface-bg: var(--color-mid);
  --color-surface-bg-interact: var(--color-mid-shade);
  --color-surface-text: var(--color-dark);
  --color-surface-text-interact: var(--color-dark);
  --font-base: -apple-system, 'BlinkMacSystemFont', avenir next, avenir, segoe ui, helvetica neue, helvetica, cantarell,
    ubuntu, roboto, noto, arial, sans-serif;
  --font-display: var(--font-base);
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-bold: 700;
  --font-weight-black: 900;
  --focus-ring: 2px solid currentcolor;
  --focus-ring-offset: 2px;
}

body {
  font-family: var(--font-base);
  font-size: var(--text-size-base);
  line-height: var(--leading);
  color: var(--color-global-text);
  background: var(--color-global-bg);
}

.grid {
  display: grid;
  grid-template-columns: repeat(var(--grid-placement, auto-fill), minmax(var(--grid-min-item-size, 16rem), 1fr));
  gap: var(--space-gutter, var(--space-s-l));
}

.button {
  display: inline-flex;
  gap: var(--button-gap, var(--space-gutter));
  padding: var(--button-padding, 0.8em 1.5em);
  font-weight: var(--button-font-weight, var(--font-weight-medium));
  line-height: var(--button-leading, var(--leading-fine));
  color: var(--button-text, var(--color-surface-text));
  text-decoration: none;
  text-transform: var(--button-text-transform, uppercase);
  letter-spacing: var(--button-kerning, var(--kerning-loose));
  background: var(--button-bg, var(--color-surface-bg));
  border-radius: var(--button-radius, 0);
}

.button:hover {
  color: var(--button-interact-text, var(--color-surface-text-interact));
  background: var(--button-interact-bg, var(--color-surface-bg-interact));
}

React Design Variants​

import React, { ButtonHTMLAttributes } from 'react'

type ButtonVariant = 'filled' | 'outlined'

export type ButtonProps = {
  /**
   * the variant of the button to use
   * @default 'outlined'
   */
  variant?: ButtonVariant
} & ButtonHTMLAttributes<HTMLButtonElement>

const ButtonStyles: { [key in ButtonVariant]: React.CSSProperties } = {
  filled: {
    backgroundColor: 'blue', // Change this to your filled button color
    color: 'white',
  },
  outlined: {
    border: '2px solid blue', // Change this to your outlined button color
    backgroundColor: 'transparent',
    color: 'blue',
  },
}

export function Button({
  variant = 'outlined',
  children,
  style,
  ...rest
}: ButtonProps) {
  return (
    <button
      type="button"
      style={{
        ...ButtonStyles[variant],
        padding: '10px 20px',
        borderRadius: '5px',
        cursor: 'pointer',
        ...style,
      }}
      {...rest}
    >
      {children}
    </button>
  )
}

Design Tokens Naming Convention​

Design Principles​

Cicada Principle​

禅原则:

当用户注意到一个有辨识度的特征 (比如木纹上的节疤) 在以固定的规律循环重复时, 那它试图营造的自然随机性就会立刻崩塌. 使用 CSS 实现形状时, 应尽可能地重现大自然的随机性.

Fitts Law​

费茨定律:

人机交互和人体工程学中人类活动的模型, 它预测了从任意位置快速移动到一个目标位置所需的时间, 由 2 个位置的距离（D）和目标大小（S）有关, 正比于 D, 反比于 S:

  • 关联性强的 UI 放置在一起.
  • 大拇指点击热区.
  • 屏幕边界视为无限大 (容易到达).
  • 关机滑动距离长.
  • 利用透明边框或伪元素扩大可点击区域 (hit area).

米勒定律​

人的短时记忆能力广度为 7±2 个信息块:

  • 手机号/银行卡号/超大数字分段放置, 信息分层 e.g 134 9999 9999, 999, 999, 999.
  • 文章布局时增大段落间 margin, 改变部分文字的粗细/字体/颜色.
  • 导航/选项卡不超过 9 个 (超过 9 个可使用 dropdown/subMenu).

席克定律​

用户所面临的选择数量越多, 做出选择所花费的时间就越长, 在人机交互的界面中选项越多, 意味着用户做出决策的时间越长:

  • 减少选项并提供默认值.
  • 分类分层.
  • 分步分页 (大部分手机应用注册界面).

泰斯勒定律​

泰斯勒定律又称复杂性守恒定律, 该定律认为每一个过程都有其固有的复杂性, 这个复杂性存在一个临界点, 超过了这个点就不能再简化了, 你只能将固有的复杂性从一个地方移动到另外一个地方:

  • 智能手机: 按键的复杂度转为手机操作系统的复杂度.
  • 智能推荐: 用户自己选择筛选条件的复杂度转为人工智能算法的复杂度.

Components Design Principles​

HomePage User Experience​

UX research point out that:

  • Feature a Broad Range of Product Types (6% Don’t).
  • Avoid Overly Aggressive and Distracting Ads (59% Don’t).
  • Implement Carousels Carefully (75% Don’t).
  • Assist the Selection of a Well-Defined Scope (62% Don’t).
  • Invest in Bespoke Imagery and Design (19% Don’t).
  • Make the Search Field Immediately Obvious (22% Don’t).
  • Implement Country & Language Selection Carefully (35% Don’t).
  • Ensure Visual Hit Areas Match the Actual Hit Areas (43% Don’t).

NNGroup article homepage design principles:

  • Ensure Easy Access to the Homepage:
    • Ensure every page includes both implicit and explicit links to the homepage.
    • Use a simple and predictable URL for your site.
    • Signpost your homepage by making it visually distinct from other pages.
  • Communicate Who You Are and What You Do:
    • Display the company name and logo prominently in the top left corner of the homepage.
    • Include a tagline that explicitly conveys what your site or company does.
    • Emphasize the unique value your site brings to your users, as well as how it differentiates from competitors.
    • Ensure that featured imagery accurately reflects your brand.
  • Reveal Content Through Examples:
    • Place the most important content above the fold, and lead users down the page when there is more content to see.
    • Provide specific examples of your site's content.
  • Prompt Actions and Navigation:
    • Include clear, descriptive link labels that resonate with your users.
    • Emphasize high-priority tasks with a clear visual hierarchy.
    • Locate primary navigation in a highly noticeable place.
  • Keep Homepages Simple:
    • Opt for simple, standard homepage designs.
    • Minimize motion and animation.
    • Provide immediate access to content.
    • Avoid popup windows and splash screens unless legally required.

Form Design Principles​

Buttons Placement Principles​

Principles:

  • Align the primary button to the left edge of the inputs.
  • Put the back button above the form.
  • Put tangentially related actions above the form.
  • Place extra buttons based on what they do.
  • In some single field forms put the button next to the input (e.g search button).
  • Put buttons on multi select forms above the form.