Viewport units in CSS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding viewport width (vw) unit

If the browser window width is 1000px, what will be the computed width of a box styled with width: 10vw;?

A 1000px

B 10px

C 100px

D 10,000px

💡 Hint

Remember that 1vw equals 1% of the viewport width.

The vw unit means 1% of the viewport width. So 10vw is 10% of 1000px, which is 100px.

📝 Syntax

intermediate

Which CSS rule correctly sets height to 50% of viewport height?

Select the CSS rule that sets an element's height to half the viewport height.

A height: 50vh;

B height: 50vw;

C height: 50%;

D height: 50pxvh;

💡 Hint

vh means viewport height, vw means viewport width.

vh is the unit for viewport height. So height: 50vh; sets height to 50% of viewport height.

❓ rendering

advanced

What is the visible height of the box on a 800px tall viewport?

Given this CSS, what is the visible height of the <div> box?

div {
  height: 50vh;
  max-height: 300px;
}

CSS

<div>Box</div>

A 50px

B 300px

C 400px

D 800px

💡 Hint

Check which is smaller: 50vh or max-height.

50vh of 800px is 400px, but max-height limits it to 300px, so height is 300px.

❓ selector

advanced

Which CSS selector targets elements with width less than 50vw?

Which CSS media query correctly applies styles only when viewport width is less than 50vw?

A @media (max-width: 50vw) { /* styles */ }

B @media (max-width: 50px) { /* styles */ }

C @media (max-width: 50vh) { /* styles */ }

D @media (max-width: 50%) { /* styles */ }

💡 Hint

Media queries accept viewport units like vw and vh.

max-width: 50vw means styles apply when viewport width is less than 50% of viewport width, which is logically consistent.

❓ accessibility

expert

How to ensure text remains readable on small viewports using viewport units?

You want text size to scale with viewport width but never become smaller than 1rem for readability. Which CSS rule achieves this?

A font-size: clamp(2vw, 1rem, 5vw);

B font-size: min(1rem, 2vw);

C font-size: 2vw;

D font-size: max(1rem, 2vw);

💡 Hint

Use CSS functions to set minimum font size.

max(1rem, 2vw) means font size is at least 1rem, scaling up with viewport width but never smaller than 1rem.

Practice

1. What does the CSS unit 1vw represent?

easy

A. 1% of the viewport's width

B. 1% of the viewport's height

C. 1 pixel

D. 1% of the parent element's width

Solution

1. Step 1: Understand viewport width unit

   The unit vw stands for viewport width, so 1vw equals 1% of the browser window's width.

2. Step 2: Compare with other units

   Unlike vh which is viewport height, vw relates only to width, not height or pixels.

3. Final Answer:

   1% of the viewport's width -> Option A

4. Quick Check:

   1vw = 1% viewport width [OK]

Hint: Remember vw = viewport width percent [OK]

Common Mistakes:

• Confusing vw with vh
• Thinking vw is pixels
• Mixing viewport units with parent size

2. Which of the following is the correct CSS syntax to set an element's height to 50% of the viewport height?

easy

A. height: 50vw;

B. height: 50vmax;

C. height: 50vmin;

D. height: 50vh;

Solution

1. Step 1: Identify viewport height unit

   The unit vh means viewport height, so 50vh means 50% of the viewport height.

2. Step 2: Check other units

   vw is viewport width, vmin is the smaller of width or height, and vmax is the larger. Only vh sets height relative to viewport height directly.

3. Final Answer:

   height: 50vh; -> Option D

4. Quick Check:

   Use vh for viewport height in CSS [OK]

Hint: Use vh for height, vw for width [OK]

Common Mistakes:

• Using vw for height
• Confusing vmin and vmax
• Forgetting semicolon in CSS

3. Given this CSS:

div {
  width: 10vw;
  height: 20vh;
}

If the browser window is 1000px wide and 800px tall, what will be the div's width and height in pixels?

medium

A. Width: 200px, Height: 400px

B. Width: 10px, Height: 20px

C. Width: 100px, Height: 160px

D. Width: 1000px, Height: 800px

Solution

1. Step 1: Calculate width from vw

   10vw means 10% of viewport width. 10% of 1000px = 100px.

2. Step 2: Calculate height from vh

   20vh means 20% of viewport height. 20% of 800px = 160px.

3. Final Answer:

   Width: 100px, Height: 160px -> Option C

4. Quick Check:

   vw and vh convert to % of viewport size [OK]

Hint: Multiply vw/vh % by viewport pixels [OK]

Common Mistakes:

• Mixing width and height values
• Calculating percentages incorrectly
• Confusing vh with vw

4. This CSS code is intended to make a box fill the smaller dimension of the viewport, but it doesn't work as expected:

.box {
  width: 50vmin;
  height: 50vmin;
}

What is the likely problem?

medium

A. The viewport units need a unit like px after vmin

B. The viewport size might be changing, causing unexpected results

C. vmin is not supported by browsers

D. The CSS syntax is correct; problem is elsewhere

Solution

1. Step 1: Understand vmin behavior

   vmin uses the smaller of viewport width or height. If viewport changes size (like resizing window), the box size changes too.

2. Step 2: Identify dynamic viewport effect

   Because viewport size can change, the box size changes dynamically, which may look like it doesn't work as expected.

3. Final Answer:

   The viewport size might be changing, causing unexpected results -> Option B

4. Quick Check:

   vmin depends on viewport size changes [OK]

Hint: Remember viewport units react to window resizing [OK]

Common Mistakes:

• Thinking vmin needs px unit
• Assuming viewport units are fixed
• Believing vmin is unsupported

5. You want a square element that always fits inside the viewport without scrolling, using viewport units. Which CSS rule ensures the square's size adapts to the smaller viewport dimension?

hard

A. width: 100vmin; height: 100vmin;

B. width: 100vw; height: 100vh;

C. width: 100vmax; height: 100vmax;

D. width: 100%; height: 100%;

Solution

1. Step 1: Understand vmin and vmax

   vmin is the smaller of viewport width or height, vmax is the larger.

2. Step 2: Choose unit for fitting inside viewport

   To fit inside viewport without scrolling, use vmin so the square fits the smaller dimension.

3. Step 3: Confirm width and height match

   Setting both width and height to 100vmin creates a square that fits inside viewport.

4. Final Answer:

   width: 100vmin; height: 100vmin; -> Option A

5. Quick Check:

   Use vmin for square fitting smaller viewport side [OK]

Hint: Use vmin for size based on smaller viewport side [OK]

Common Mistakes:

• Using vmax causes overflow
• Using 100% depends on parent size
• Confusing vw/vh with vmin/vmax