First Move (11~18) - Code, Learn, Build
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First Move (11~18) - Code, Learn, Build

Structured, level-based technology learning paths from foundational exploration to industry mastery.

Learning Domains

  • Python Programming (Active)
  • Computer Science Core
  • Web Development
  • AI & Machine Learning

Platform Architecture

  • Level-Based Progression
  • Decoupled Content Schema
  • Modular Code Execution Engine
  • Curated Official Resources

© 2026 First Move (11~18) • CODE • LEARN • BUILD. Built with Next.js App Router.

Readability & Accessibility First

← HTML5 & Modern CSS Layout Systems|Level 2: CSS Box Model, Flexbox & Grid Systems

3. CSS Box Model & 1D Layouts with Flexbox

Lesson 3 of 6
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CSS Box Model & 1D Layouts with Flexbox

Understand border-box dimensions, margin collapse, flex-direction, justify-content, align-items, and flex-grow/shrink/basis rules.

The CSS Box Model & Flexbox Mechanics

### The CSS Box Model Every element in CSS is rendered as a rectangular box comprising: 1. **Content**: Text or media. 2. **Padding**: Internal space inside the border. 3. **Border**: Outer line boundary. 4. **Margin**: External space separating adjacent elements. Using `box-sizing: border-box` ensures padding and border widths are included INSIDE total element width.
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