CSS Styling and Animations - GitHub Profile README

Overview

The GitHub profile README project uses a CSS-in-JS approach where styles are embedded directly in SVG <foreignObject> elements. This allows for dynamic styling with full CSS support including animations, custom properties, and media queries.

CSS-in-JS Architecture

SVG Wrapper Function

All sections use a common SVG wrapper that injects styles:

const svg = (styles: string, html: string, attributes: Attributes) => {
  if (!attributes.width) attributes.width = "100%";
  return `
    <svg xmlns="http://www.w3.org/2000/svg" fill="none" ${attr(attributes)}>
      <foreignObject width="100%" height="100%">
        <div xmlns="http://www.w3.org/1999/xhtml">
          <style>${styles}</style>
          ${html}
        </div>
      </foreignObject>
    </svg>`;
};

Reference: src/render.ts:89-100

Shared Base Styles

A comprehensive set of shared styles is defined once and reused across all sections:

export const shared = /* css */ `
  @font-face { ... }
  :root { ... }
  [data-theme="dark"] { ... }
  [data-theme="light"] { ... }
  /* Common styles */
`;

Reference: src/render.ts:102-290

Section-Specific Styles

Each section combines shared styles with its own custom CSS:

const styles = /*css*/ `
  ${shared}
  
  :root {
    --size-height: ${props.height};
    /* Section-specific variables */
  }
  
  /* Section-specific styles */
`;

Reference: src/render.ts:308-428 (main section example)

Animation System

The project features a sophisticated animation system with multiple effects.

Fade-In Animation

The primary animation for revealing content:

.fade-in {
  will-change: opacity;
  animation-name: fade-in;
  animation-fill-mode: both;
  animation-duration: var(--duration, var(--default-duration));
  animation-timing-function: var(--ease, ease-out);
  animation-delay: var(--delay, var(--default-delay));
}

@keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

Reference: src/render.ts:238-259

Animation Timing

Default timing variables:

:root {
  --default-delay: 1s;
  --default-duration: 1.55s;
  --default-stagger: 0.1s;
}

Reference: src/render.ts:164-167

Staggered Animations

Animations are orchestrated with calculated delays:

--animate-in-menu-delay: calc(var(--default-delay) + var(--default-stagger) * 0);
--animate-in-links-delay: calc(var(--default-delay) + var(--default-stagger) * 1);
--animate-in-contributions-delay: calc(var(--default-delay) + var(--default-stagger) * 5);
--animate-in-readme-delay: calc(var(--default-delay) + var(--default-stagger) * 6);
--animate-in-copy-delay: calc(var(--default-delay) + var(--default-stagger) * 7);
--animate-in-graph-delay: calc(var(--default-delay) + var(--default-stagger) * 17);

Reference: src/render.ts:169-176

Character-by-Character Animation

Text is animated one character at a time:

BODY_COPY.split("")
  .map((c, i) => `<span class="fade-in" style="--i: ${i};">${c}</span>`)
  .join("")

.intro span {
  contain: content;
  --duration: 980ms;
  --delay: calc(var(--animate-in-copy-delay) + var(--i) * 10ms);
}

Reference: src/render.ts:446-448, 335-338

Shine Animation

A gradient shine effect for text:

.shine {
  background-color: var(--color-text);
  background-image: linear-gradient(-75deg,
    transparent 0%,
    rgba(255, 255, 255, 0.18) 15%,
    transparent 25%
  );
  background-size: 200%;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  text-fill-color: transparent;

  animation-name: shine;
  animation-duration: 14s;
  animation-iteration-count: infinite;
}

@keyframes shine {
  0% {
    background-position: 200%;
  }
  10% {
    background-position: 0%;
  }
  to {
    background-position: 0%;
  }
}

Reference: src/render.ts:261-289

Scroll Animation

The contribution graph scrolls horizontally:

.years {
  animation-name: scroll, fade-in;
  animation-timing-function: linear, ease-out;
  animation-duration: calc(30s + (var(--_w) * 0.06s)), 2.5s;
  animation-fill-mode: both, both;
  animation-delay: 2s, var(--animate-in-graph-delay);
}

@keyframes scroll {
  0% {
    transform: translateX(60px);
  }
  100% {
    transform: translateX(calc(-100% + 100cqw));
  }
}

Reference: src/render.ts:371-384 Key features:

Duration scales with content width
Combines scroll and fade-in animations
Uses CSS container queries (100cqw)

Rotate Animation

Link arrows rotate playfully:

.link__arrow {
  animation-name: rotate;
  animation-duration: 5s;
  animation-timing-function: ease-in-out;
  animation-iteration-count: infinite;
  animation-delay: ${Math.random() * 5}s;
}

@keyframes rotate {
  0% {
    transform: rotate(0deg);
  }
  10%,
  100% {
    transform: rotate(360deg);
  }
}

Reference: src/render.ts:577-596 Features:

Random delays for variety
Quick rotation (10% of duration)
Long pause between rotations

Performance Optimizations

CSS Containment

Multiple containment strategies are used:

/* Strict containment for wrapper */
.wrapper {
  contain: strict;
}

/* Content containment for text elements */
.label {
  contain: content;
}

/* Layout containment with auto-visibility */
.year {
  contain: strict;
  content-visibility: auto;
}

Reference: src/render.ts:210, 228, 387-388 Types of containment:

strict: Size, layout, style, and paint containment
content: Layout, style, and paint containment
Combined with content-visibility: auto for lazy rendering

Hardware Acceleration

.years {
  will-change: transform;
  backface-visibility: hidden;
  transform: translateZ(0);
}

Reference: src/render.ts:367-369

Container Queries

The system uses container queries for responsive sizing:

.wrapper {
  container-type: inline-size;
}

/* Use container width */
transform: translateX(calc(-100% + 100cqw));

Reference: src/render.ts:212, 382

Responsive Design

Breakpoints

const BP_MEDIUM = 550;
const BP_LARGE = 700;

Media Queries

@media (width > 550px) {
  .intro {
    grid-area: 1 / 3 / span 1 / span 4;
    font-size: 22px;
  }
}

@media (width > 700px) {
  .intro {
    grid-area: 1 / 4 / span 1 / span 3;
  }
}

Reference: src/render.ts:340-350

Custom Properties (CSS Variables)

Dynamic Variables

Styles use custom properties for dynamic values:

:root {
  --rows: ${props.dots.rows};
  --size-width: 100cqw;
  --size-height: ${props.height};
  --size-dot-gap: ${props.dots.gap};
  --size-dot: ${props.dots.size};
  --size-year-gap: ${props.year.gap};
  --size-label-height: 20;
}

Reference: src/render.ts:311-318

Calculated Values

/* Dot grid dimensions */
grid-template-rows: repeat(var(--rows), calc(var(--size-dot) * 1px));
gap: calc(var(--size-dot-gap) * 1px);

/* Border radius based on dot size */
border-radius: calc(var(--size-dot) * 0.15 * 1px);

Reference: src/render.ts:404-406, 420

Browser-Specific Styling

Firefox Fallbacks

Special handling for Firefox:

/* Hide everything in Firefox by default - show fallback instead */
@-moz-document url-prefix() {
  .wrapper {
    display: none;
  }
}

/* Allow specific sections in Firefox */
@-moz-document url-prefix() {
  .wrapper {
    display: block;
  }
}

Reference: src/render.ts:221-225, 561-565

Modifying Styles

Changing Animation Speed

Adjust timing variables:

:root {
  --default-delay: 0.5s;      /* Start sooner */
  --default-duration: 1s;      /* Faster transitions */
  --default-stagger: 0.05s;    /* Tighter sequence */
}

Customizing Dot Appearance

Modify dot styling:

.dot {
  border-radius: 50%;  /* Circular instead of rounded square */
  border: none;        /* Remove borders */
}

Adding New Animations

Define the keyframes:

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

Apply to elements:

.element {
  animation: bounce 2s ease-in-out infinite;
}

Typography Adjustments

Change font sizes across breakpoints:

.intro {
  font-size: 16px;  /* Mobile */
}

@media (width > 550px) {
  .intro {
    font-size: 20px;  /* Tablet */
  }
}

@media (width > 700px) {
  .intro {
    font-size: 24px;  /* Desktop */
  }
}

Best Practices

Use CSS containment for performance on large datasets
Leverage custom properties for dynamic, theme-aware styling
Apply will-change sparingly - only on animating elements
Use container queries instead of viewport-based media queries when possible
Test animations at different speeds using browser dev tools
Consider reduced motion preferences for accessibility

Performance Tips

Avoid animating expensive properties - stick to opacity and transform
Use animation-fill-mode: both to prevent flashing
Apply backface-visibility: hidden for smoother transforms
Use content-visibility: auto for off-screen content
Batch style updates by combining animations when possible

​Overview

​CSS-in-JS Architecture

​SVG Wrapper Function

​Shared Base Styles

​Section-Specific Styles

​Animation System

​Fade-In Animation

​Animation Timing

​Staggered Animations

​Character-by-Character Animation

​Shine Animation

​Scroll Animation

​Rotate Animation

​Performance Optimizations

​CSS Containment

​Hardware Acceleration

​Container Queries

​Responsive Design

​Breakpoints

​Media Queries

​Custom Properties (CSS Variables)

​Dynamic Variables

​Calculated Values

​Browser-Specific Styling

​Firefox Fallbacks

​Modifying Styles

​Changing Animation Speed

​Customizing Dot Appearance

​Adding New Animations

​Typography Adjustments

​Best Practices

​Performance Tips