Learn CSS in 10 DaysDay 8: Responsive Design
Chapter 8Learn CSS in 10 Days

Day 8: Responsive Design

What You Will Learn Today

  • The principles of responsive design
  • The viewport meta tag
  • Media queries and breakpoints
  • The mobile-first approach
  • Responsive images and media
  • The clamp() function for fluid typography
  • Container queries

What is Responsive Design?

Responsive design is an approach to web design that ensures your pages look great on every screen size -- from phones to ultra-wide monitors.

flowchart LR
    subgraph Devices["Different Devices"]
        Mobile["Mobile<br>up to 767px"]
        Tablet["Tablet<br>768 - 1023px"]
        Desktop["Desktop<br>1024px+"]
    end
    style Mobile fill:#22c55e,color:#fff
    style Tablet fill:#f59e0b,color:#fff
    style Desktop fill:#3b82f6,color:#fff

The Three Pillars

Pillar Description
Fluid Layouts Use %, fr, and flexible units instead of fixed widths
Media Queries Apply different styles based on screen characteristics
Flexible Media Images and videos that resize automatically

The Viewport Meta Tag

This tag is a prerequisite for responsive design.

<meta name="viewport" content="width=device-width, initial-scale=1.0">

Required: Without this meta tag, mobile browsers will render the page at a desktop width and scale it down, making your media queries useless.

Media Queries

Basic Syntax

@media (max-width: 768px) {
    .container {
        padding: 16px;
    }
}

@media (min-width: 1024px) {
    .container {
        max-width: 1200px;
    }
}

Common Breakpoints

/* Smartphones */
@media (max-width: 767px) { ... }

/* Tablets */
@media (min-width: 768px) and (max-width: 1023px) { ... }

/* Desktops */
@media (min-width: 1024px) { ... }

/* Large screens */
@media (min-width: 1280px) { ... }
Breakpoint Target Device
640px Small smartphones
768px Tablets
1024px Laptops
1280px Desktops
1536px Large displays

The Mobile-First Approach

Write styles for the smallest screen first, then layer on enhancements for larger screens using min-width queries.

/* Mobile (default styles) */
.grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
}

/* Tablets and up */
@media (min-width: 768px) {
    .grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Desktops and up */
@media (min-width: 1024px) {
    .grid {
        grid-template-columns: repeat(3, 1fr);
        gap: 24px;
    }
}

flowchart LR
    Mobile["Mobile<br>1 column"] -->|"768px"| Tablet["Tablet<br>2 columns"]
    Tablet -->|"1024px"| Desktop["Desktop<br>3 columns"]
    style Mobile fill:#22c55e,color:#fff
    style Tablet fill:#f59e0b,color:#fff
    style Desktop fill:#3b82f6,color:#fff

Why mobile-first? Mobile users make up the majority of web traffic. Starting with the minimal layout and progressively enhancing it is more efficient and produces cleaner CSS.

Responsive Images

img {
    max-width: 100%;
    height: auto;
}

Responsive Video Embeds

.video-wrapper {
    position: relative;
    padding-bottom: 56.25%;    /* 16:9 aspect ratio */
    height: 0;
}

.video-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

Modern approach: The aspect-ratio property simplifies this significantly.

.video-wrapper {
    aspect-ratio: 16 / 9;
    width: 100%;
}

.video-wrapper iframe {
    width: 100%;
    height: 100%;
}

Responsive Navigation

/* Mobile: vertical stack */
.nav-links {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* Desktop: horizontal row */
@media (min-width: 768px) {
    .nav-links {
        flex-direction: row;
        gap: 24px;
    }
}

Responsive Typography with clamp()

The clamp() function sets a value that scales fluidly between a minimum and maximum.

h1 {
    /* Minimum 2rem, preferred 5vw, maximum 4rem */
    font-size: clamp(2rem, 5vw, 4rem);
}

p {
    font-size: clamp(1rem, 2.5vw, 1.25rem);
}
Argument Purpose
Minimum The value will never go below this
Preferred Scales with the viewport
Maximum The value will never exceed this

Best practice: clamp() lets you create smoothly scaling typography without any media queries at all.

Container Queries

Instead of responding to the viewport size, container queries respond to the size of a parent container.

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

@container (min-width: 400px) {
    .card {
        display: flex;
        gap: 16px;
    }
}

@container (min-width: 600px) {
    .card {
        font-size: 1.125rem;
    }
}

Note: Container queries are supported in all modern browsers and are especially useful for reusable components that may appear in containers of varying widths.

Practice: Responsive Landing Page

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --color-primary: #3b82f6;
    --max-width: 1200px;
}

body {
    font-family: system-ui, sans-serif;
    line-height: 1.6;
    color: #1e293b;
}

img {
    max-width: 100%;
    height: auto;
}

/* Header */
.header {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
    padding: 16px;
}

/* Hero */
.hero {
    text-align: center;
    padding: 48px 16px;
}

.hero h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
    margin-bottom: 16px;
}

/* Card Grid */
.cards {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
    padding: 32px 16px;
    max-width: var(--max-width);
    margin: 0 auto;
}

/* Footer */
.footer {
    background: #1e293b;
    color: #94a3b8;
    text-align: center;
    padding: 32px 16px;
}

/* Tablet and up */
@media (min-width: 768px) {
    .header {
        flex-direction: row;
        justify-content: space-between;
        padding: 16px 32px;
    }

    .hero {
        padding: 80px 32px;
    }

    .cards {
        grid-template-columns: repeat(2, 1fr);
        gap: 24px;
        padding: 48px 32px;
    }
}

/* Desktop and up */
@media (min-width: 1024px) {
    .cards {
        grid-template-columns: repeat(3, 1fr);
    }
}

Summary

Concept Description
Responsive Design Adapts to any screen size
Media Queries Conditional styles with @media
Mobile-First Build from small to large with min-width
clamp() Fluid values with min, preferred, and max
Container Queries Styles based on parent container size
max-width: 100% Makes images responsive

Key Takeaways

  1. The viewport meta tag is essential
  2. Use the mobile-first approach with min-width queries
  3. clamp() enables media-query-free responsive sizing
  4. auto-fit + minmax() creates flexible grids automatically

Exercises

Exercise 1: Basics

Create a grid that displays 1 column on mobile, 2 on tablet, and 3 on desktop.

Exercise 2: Intermediate

Build a navigation that stacks vertically on mobile and displays horizontally on desktop.

Challenge

Create an entirely responsive page using only clamp(), auto-fit, and minmax() -- no media queries allowed.

References

Next up: In Day 9, you will learn about Transitions and Animations -- how to bring your designs to life with smooth, performant motion using pure CSS.