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Updated: 2026年5月31日

Font Size

Original task (JA): フォントサイズ

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Conclusion

Font Size — free browser-based HTML/CSS/JS practice

■ What this exercise teaches pのフォントサイズを1.2remにしてください。

Why it matters in real projects

remはルートのフォントサイズに対する相対値です。 Similar patterns appear daily in code review and production UI work.

Step-by-step workflow

1. Read the guide and understand the goal of "Font Size" 2. Review the HTML/CSS/JS editor pane and start from the starter code 3. Open hints if stuck; compare your diff with the sample solution 4. Click Run and inspect preview/console output 5. Auto-check looks for output containing: font-size, 1.2. 6. After success, continue with adjacent exercises in the same category

Core concept explained

remはルートのフォントサイズに対する相対値です。

Technical focus

Key HTML elements in this task: p, style.

Hint before you peek at the solution

font-size を使います。

Sample solution walkthrough

The solution uses HTML tags such as p, style. Check nesting and closing tags. CSS properties include font-size. Watch selector spelling and specificity. Explanation: remはルートのフォントサイズに対する相対値です。 Hint recap: font-size を使います。

Solution code

📝 Sample code
<p>段落</p>
<style>p { font-size: 1.2rem; }</style>

Common mistakes for this exact task

・Skipping the hint: font-size を使います。

Troubleshooting

Q: Preview does not change after Run A: Ensure you edited the HTML/CSS/JS pane and clicked Run. Q: Looks correct but check fails A: Auto-check looks for output containing: font-size, 1.2. Look for typos, full-width spaces, or unclosed tags. Q: Console shows errors A: Open DevTools Console and fix bracket/quote mismatches at the reported line. Q: Hard to type on mobile A: Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Interview / portfolio tips

・Explain the techniques in "Font Size" in your own words within 30 seconds ・Practice walking through each line of the sample solution on a whiteboard ・Be ready to discuss tags: p, style ・Discuss CSS properties: font-size ・Prepare one alternative approach and why you chose this one

What to do after you pass

Move to the next exercise in the css-basic track, then continue the learning roadmap at /en/learning/css-basic/.

Keywords

Free hands-on exercise covering フォントサイズ, css-basic, 入門, p, style, font-size, font size—search-friendly guide for Font Size.

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■ Exercise task

pのフォントサイズを1.2remにしてください。

Hint if stuck

font-size を使います。

10pt

フォントサイズ

pのフォントサイズを1.2remにしてください。

エラーをクリックで該当行をハイライト。✕=エラー ⚠=警告 ›=ログ。

Roadmap · All guides

Deep dive

"Font Size" is a 入門-level HTML/CSS/JS exercise. pのフォントサイズを1.2remにしてください。 Run it in-browser with automatic checking.

remはルートのフォントサイズに対する相対値です。 Similar patterns appear daily in code review and production UI work.

Pair this with the css-basic roadmap. Exercise #20 reinforces core css-basic skills.

Step-by-step workflow

  1. Read the guide and understand the goal of "Font Size"
  2. Review the HTML/CSS/JS editor pane and start from the starter code
  3. Open hints if stuck; compare your diff with the sample solution
  4. Click Run and inspect preview/console output
  5. Auto-check looks for output containing: font-size, 1.2.
  6. After success, continue with adjacent exercises in the same category

How to read the sample solution

The solution uses HTML tags such as p, style. Check nesting and closing tags. CSS properties include font-size. Watch selector spelling and specificity. Explanation: remはルートのフォントサイズに対する相対値です。 Hint recap: font-size を使います。

Real-world & career relevance

CSS basics underpin designer collaboration and frameworks like Tailwind. Color, spacing, and type define brand consistency.

Common mistakes

  • Skipping the hint: font-size を使います。
  • Confusing margin and padding
  • Missing # in hex colors
  • Forgetting . for class selectors

Troubleshooting

Preview does not change after Run
Ensure you edited the HTML/CSS/JS pane and clicked Run.
Looks correct but check fails
Auto-check looks for output containing: font-size, 1.2. Look for typos, full-width spaces, or unclosed tags.
Console shows errors
Open DevTools Console and fix bracket/quote mismatches at the reported line.
Hard to type on mobile
Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Interview & portfolio tips

  • Explain the techniques in "Font Size" in your own words within 30 seconds
  • Practice walking through each line of the sample solution on a whiteboard
  • Be ready to discuss tags: p, style
  • Discuss CSS properties: font-size
  • Prepare one alternative approach and why you chose this one

Glossary

color
CSS property for text color.
padding
Inner spacing inside an element.
margin
Outer spacing around an element.

Keywords covered on this page

Free hands-on exercise covering フォントサイズ, css-basic, 入門, p, style, font-size, font size—search-friendly guide for Font Size.

Related dev tools

Learning roadmap

Learning roadmap →

Related exercises

Frequently asked questions

Is "フォントサイズ" free?

This exercise is free and runs entirely in your browser. No account or credit card required.

Difficulty and time?

"フォントサイズ" is level "入門". Read the guide first; beginners can usually finish within 30 minutes. Allow 5–15 minutes per exercise. Use hints, then the solution if stuck.

What after a correct answer?

After a correct answer, use "Next exercise". When you finish a category, continue on the learning roadmap.

Works on mobile?

Works on mobile browsers, but typing code is easier on a desktop.

Where are other exercises?

All exercises: /en/learn/ with category filters.

Key takeaway for "フォントサイズ"?

remはルートのフォントサイズに対する相対値です。 Hint: font-size を使います。

Where does css-basic fit?

CSS basics underpin designer collaboration and frameworks like Tailwind. Color, spacing, and type define brand consistency.

Step-by-step for "Font Size"?

1. Read the guide and understand the goal of "Font Size"
2. Review the HTML/CSS/JS editor pane and start from the starter code
3. Open hints if stuck; compare your diff with the sample solution
4. Click Run and inspect preview/console output
5. Auto-check looks for output containing: font-size, 1.2.
6. After success, continue with adjacent exercises in the same category

How to read the sample solution?

The solution uses HTML tags such as p, style. Check nesting and closing tags.

CSS properties include font-size. Watch selector spelling and specificity.

Explanation: remはルートのフォントサイズに対する相対値です。

Hint recap: font-size を使います。

Something is not working?

Preview does not change after Run → Ensure you edited the HTML/CSS/JS pane and clicked Run.
Looks correct but check fails → Auto-check looks for output containing: font-size, 1.2. Look for typos, full-width spaces, or unclosed tags.
Console shows errors → Open DevTools Console and fix bracket/quote mismatches at the reported line.
Hard to type on mobile → Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Career / interview angle?

Explain the techniques in "Font Size" in your own words within 30 seconds Practice walking through each line of the sample solution on a whiteboard Be ready to discuss tags: p, style Discuss CSS properties: font-size Prepare one alternative approach and why you chose this one

Can I change the starter code?

Yes—if it works. Understanding the starter first, then adding minimal diffs, speeds up learning.

What do the points mean?

10pt is a difficulty hint, not a score you must maximize.