Using variables in CSS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a CSS variable for the main color.

CSS

:root { --main-color: [1]; }

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

Acolor

Bblue

Cmain-color

D#3498db

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name as a value instead of a color.

Forgetting the colon after the variable name.

The correct way to declare a CSS variable is to use a valid color value like a hex code.

2fill in blank

medium

Complete the code to use the CSS variable for background color.

CSS

body { background-color: [1](--main-color); }

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

Acolor

Bvar

Cget

Duse

Attempts:

3 left

💡 Hint

Common Mistakes

Writing the variable name without var().

Using incorrect function names like use() or get().

To use a CSS variable, you write var(--variable-name).

3fill in blank

hard

Fix the error in the CSS variable usage for text color.

CSS

p { color: [1](--text-color); }

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

Avar

Btext

Ccolor

Duse

Attempts:

3 left

💡 Hint

Common Mistakes

Using the variable name directly without var().

Using incorrect function names.

The correct function to use a CSS variable is var().

4fill in blank

hard

Fill both blanks to declare and use a CSS variable for font size.

CSS

:root { [1]-font-size: 1.2rem; } h1 { font-size: [2](--main-font-size); }

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

A--main

Bfont

Cvar

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the dashes in the variable name.

Not using var() to access the variable.

CSS variables are declared with names starting with -- and used with var().

5fill in blank

hard

Fill all three blanks to declare variables and use them for margin and padding.

CSS

:root { [1]-margin: 1rem; [2]-padding: 2rem; } div { margin: [3](--main-margin); padding: var(--secondary-padding); }

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

A--main

Cvar

D--secondary

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same variable name for different properties.

Not using var() to access variables.

Declare variables with --name and use var() to access them. Different variables can be declared for margin and padding.

Practice

1. What is the main purpose of CSS variables?

easy

A. To store reusable values like colors and sizes

B. To create new HTML elements

C. To write JavaScript code inside CSS

D. To add comments in CSS files

Solution

1. Step 1: Understand what CSS variables do

   CSS variables hold values that can be reused throughout the stylesheet, such as colors or font sizes.

2. Step 2: Compare options with this purpose

   Only To store reusable values like colors and sizes describes storing reusable values; others describe unrelated tasks.

3. Final Answer:

   To store reusable values like colors and sizes -> Option A

4. Quick Check:

   CSS variables = reusable values [OK]

Hint: CSS variables store values you reuse often [OK]

Common Mistakes:

• Thinking CSS variables create HTML elements
• Confusing CSS variables with JavaScript
• Believing CSS variables add comments

2. Which is the correct way to define a CSS variable for a primary color globally?

easy

A. :root { --primary-color: #3498db; }

B. body { primary-color: #3498db; }

C. :root { primary-color = #3498db; }

D. html { --primary-color #3498db; }

Solution

1. Step 1: Recall CSS variable syntax

   Variables are defined with two dashes and a colon inside a selector, usually :root for global scope.

2. Step 2: Check each option's syntax

   :root { --primary-color: #3498db; } uses correct syntax: :root { --name: value; }. Others have missing dashes, wrong selectors, or wrong assignment.

3. Final Answer:

   :root { --primary-color: #3498db; } -> Option A

4. Quick Check:

   Define variables with --name: value; inside :root [OK]

Hint: Use :root and --var-name: value; to define variables [OK]

Common Mistakes:

• Missing double dashes before variable name
• Using = instead of : for assignment
• Defining variables outside :root for global use

3. Given the CSS below, what color will the paragraph text be?

:root { --main-color: #ff0000; } p { color: var(--main-color); }

medium

A. Blue

B. Green

C. Black

D. Red

Solution

1. Step 1: Identify the variable value

   The variable --main-color is set to #ff0000, which is red.

2. Step 2: Check how the variable is used

   The paragraph's color is set using var(--main-color), so it uses the red color.

3. Final Answer:

   Red -> Option D

4. Quick Check:

   var(--main-color) = #ff0000 (red) [OK]

Hint: Match variable value hex to color name [OK]

Common Mistakes:

• Ignoring the variable and using default color
• Confusing hex codes with other colors
• Not using var() to apply variable

4. What is wrong with this CSS code?

:root { --font-size 16px; } h1 { font-size: var(--font-size); }

medium

A. Variable name should not start with dashes

B. Missing colon after --font-size in variable definition

C. Using var() incorrectly in h1 font-size

D. font-size property cannot use variables

Solution

1. Step 1: Check variable definition syntax

   The variable definition is missing a colon after --font-size; it should be --font-size: 16px;

2. Step 2: Verify usage of var()

   The usage var(--font-size) is correct in h1 font-size property.

3. Final Answer:

   Missing colon after --font-size in variable definition -> Option B

4. Quick Check:

   Variable definitions need colon after name [OK]

Hint: Variable definitions need colon after name [OK]

Common Mistakes:

• Forgetting colon in variable definition
• Thinking var() usage is wrong
• Believing variable names can't start with --

5. You want to create a theme with two colors using CSS variables: primary as blue (#0000ff) and secondary as gray (#888888). How do you apply these variables to style a button's background and border color?

hard

A. :root { --primary: blue; --secondary: gray; } button { background-color: --primary; border: 2px solid --secondary; }

B. :root { primary: #0000ff; secondary: #888888; } button { background-color: primary; border: 2px solid secondary; }

C. :root { --primary: #0000ff; --secondary: #888888; } button { background-color: var(--primary); border: 2px solid var(--secondary); }

D. button { --primary: #0000ff; --secondary: #888888; background-color: var(primary); border: 2px solid var(secondary); }

Solution

1. Step 1: Define variables globally with correct syntax

   Variables must be defined inside :root with double dashes and colon, e.g., --primary: #0000ff;

2. Step 2: Use variables with var() in button styles

   Apply variables using var(--primary) for background and var(--secondary) for border color.

3. Final Answer:

   :root { --primary: #0000ff; --secondary: #888888; } button { background-color: var(--primary); border: 2px solid var(--secondary); } -> Option C

4. Quick Check:

   Define with --name: value; use with var(--name) [OK]

Hint: Define variables in :root and use var(--name) to apply [OK]

Common Mistakes:

• Omitting -- in variable names
• Not using var() when applying variables
• Defining variables inside button instead of :root