Writing reusable CSS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a reusable CSS class that sets the text color to blue.

CSS

.text-blue { color: [1]; }

Drag options to blanks, or click blank then click option'

Ared

Bblue

Cgreen

Dyellow

Attempts:

3 left

💡 Hint

Common Mistakes

Using a color other than blue.

Forgetting the semicolon after the value.

The color property sets the text color. To make the text blue, use blue.

2fill in blank

medium

Complete the code to create a reusable CSS class that adds padding of 1rem all around.

CSS

.padded { padding: [1]; }

Drag options to blanks, or click blank then click option'

A10px

B5em

C0

D1rem

Attempts:

3 left

💡 Hint

Common Mistakes

Using pixels instead of rem units.

Setting padding to zero which removes space.

The padding property adds space inside the element. Using 1rem adds padding relative to the root font size, making it reusable and scalable.

3fill in blank

hard

Fix the error in the reusable CSS class that should center text horizontally.

CSS

.center-text { text-align: [1]; }

Drag options to blanks, or click blank then click option'

Acenter

Bleft

Cjustify

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'justify' which spreads text evenly.

Using 'left' or 'right' which aligns text to sides.

The text-align property controls horizontal alignment of text. To center text, use center.

4fill in blank

hard

Fill both blanks to create a reusable CSS class that makes text bold and adds a margin of 2rem.

CSS

.bold-margin { font-weight: [1]; margin: [2]; }

Drag options to blanks, or click blank then click option'

Abold

Bnormal

C2rem

D1rem

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'normal' font-weight which is not bold.

Using smaller margin values like 1rem.

font-weight: bold; makes text bold. margin: 2rem; adds space outside the element on all sides.

5fill in blank

hard

Fill all three blanks to create a reusable CSS class that sets background color to lightgray, text color to darkblue, and adds 1.5rem padding.

CSS

.custom-box { background-color: [1]; color: [2]; padding: [3]; }

Drag options to blanks, or click blank then click option'

Alightgray

Bdarkblue

C1.5rem

Dblack

Attempts:

3 left

💡 Hint

Common Mistakes

Using black background which is too dark.

Using padding values that are too small or missing units.

background-color: lightgray; sets a soft background. color: darkblue; sets the text color for good contrast. padding: 1.5rem; adds comfortable space inside the box.

Practice

1. What is the main benefit of using reusable CSS classes in web development?

easy

A. You can write styles once and use them many times.

B. It makes the website load slower.

C. It requires writing more code for each element.

D. It only works with inline styles.

Solution

1. Step 1: Understand the purpose of reusable CSS classes

   Reusable CSS classes allow you to write a style rule once and apply it to multiple elements, saving time and effort.

2. Step 2: Compare options to the main benefit

   Options B, C, and D describe drawbacks or incorrect uses, while You can write styles once and use them many times. correctly states the main benefit.

3. Final Answer:

   You can write styles once and use them many times. -> Option A

4. Quick Check:

   Reusable CSS = Write once, use many times [OK]

Hint: Reusable classes save time by reusing styles [OK]

Common Mistakes:

• Thinking reusable CSS slows down the site
• Confusing reusable classes with inline styles
• Believing reusable CSS requires more code

2. Which of the following is the correct syntax to define a reusable CSS class named button?

easy

A. button { color: blue; }

B. #button { color: blue; }

C. .button { color: blue; }

D. *button { color: blue; }

Solution

1. Step 1: Identify CSS selector for classes

   In CSS, classes are selected using a dot (.) before the class name.

2. Step 2: Match syntax to class selector

   .button { color: blue; } uses .button which is correct. #button { color: blue; } uses an ID selector (#), C uses an element selector, and D uses an invalid selector.

3. Final Answer:

   .button { color: blue; } -> Option C

4. Quick Check:

   Class selector starts with dot (.) [OK]

Hint: Class selectors start with a dot (.) in CSS [OK]

Common Mistakes:

• Using # instead of . for classes
• Omitting the dot before class name
• Confusing element selectors with class selectors

3. Given the CSS below, what color will the text inside the <p> tag have?

.red { color: red; } .bold { font-weight: bold; }

Hello World

medium

A. Default browser color

B. Bold only

C. Red only

D. Red and bold

Solution

1. Step 1: Analyze the applied classes

   The paragraph has two classes: red and bold. The red class sets text color to red, and bold sets font weight to bold.

2. Step 2: Combine effects of both classes

   Both styles apply together, so the text will be red and bold.

3. Final Answer:

   Red and bold -> Option D

4. Quick Check:

   Multiple classes combine styles [OK]

Hint: Multiple classes combine their styles on one element [OK]

Common Mistakes:

• Thinking only one class style applies
• Confusing color and font-weight properties
• Ignoring combined class effects

4. What is wrong with this CSS if the goal is to reuse the style for multiple buttons?

button { background-color: blue; } .button { background-color: red; }

Click me

medium

A. The class name should start with a #.

B. The element selector button and class .button conflict causing confusion.

C. Class selectors cannot be reused.

D. The CSS syntax is invalid.

Solution

1. Step 1: Understand selector types

   The selector button targets all <button> elements, while .button targets elements with class "button".

2. Step 2: Identify conflict in styles

   The paragraph has class "button" but is not a <button> element, so only .button applies. The similar names can confuse developers.

3. Final Answer:

   The element selector button and class .button conflict causing confusion. -> Option B

4. Quick Check:

   Element and class selectors with same name cause confusion [OK]

Hint: Avoid naming classes same as HTML elements [OK]

Common Mistakes:

• Using # instead of . for classes
• Assuming class selectors can't be reused
• Ignoring selector specificity and conflicts

5. You want to create a reusable CSS class for a card component that has a shadow, padding, and rounded corners. Which CSS snippet correctly combines these styles for reuse?

hard

A. .card { box-shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; border-radius: 0.5rem; }

B. #card { box-shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; border-radius: 0.5rem; }

C. card { box-shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; border-radius: 0.5rem; }

D. .card { shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; rounded: 0.5rem; }

Solution

1. Step 1: Use correct class selector syntax

   Classes use a dot (.) before the name, so .card is correct. #card { box-shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; border-radius: 0.5rem; } uses an ID selector (#), C uses an invalid element selector, and D uses incorrect CSS properties.

2. Step 2: Verify CSS properties for shadow, padding, and rounded corners

   box-shadow, padding, and border-radius are correct CSS properties. .card { shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; rounded: 0.5rem; } uses invalid properties shadow and rounded.

3. Final Answer:

   .card { box-shadow: 0 4px 6px rgba(0,0,0,0.1); padding: 1rem; border-radius: 0.5rem; } -> Option A

4. Quick Check:

   Correct class selector and CSS properties [OK]

Hint: Use dot for class and correct CSS property names [OK]

Common Mistakes:

• Using # instead of . for classes
• Using invalid CSS properties like shadow or rounded
• Omitting units or using wrong selectors