Container query preparation in SASS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does a container query do in CSS?

Which statement best describes the purpose of a container query in CSS?

A It applies styles based on the size of the element's container, not the viewport.

B It changes styles depending on the user's screen resolution only.

C It modifies styles only when the browser window is resized.

D It applies styles based on the total number of elements inside a container.

💡 Hint

Think about what 'container' means compared to 'viewport'.

Container queries let you style an element based on its container's size, not the whole screen. This helps create more flexible designs.

📝 Syntax

intermediate

Identify the correct container query syntax in Sass

Which Sass code snippet correctly uses a container query to apply styles when the container is at least 30rem wide?

A @container min-width: 30rem { .box { color: blue; } }

B @container (width >= 30rem) { .box { color: blue; } }

C @container (min-width 30rem) { .box { color: blue; } }

D @container (min-width: 30rem) { .box { color: blue; } }

💡 Hint

Look for the correct parentheses and colon usage.

The correct syntax uses parentheses around the condition with a colon separating property and value.

❓ rendering

advanced

What color will the box be when container width is 40rem?

Given the Sass code below, what color will the box have if its container is 40rem wide?

SASS

@container (min-width: 50rem) { .box { color: red; } }
@container (min-width: 30rem) { .box { color: green; } }
.box { color: black; }

A green

B black

C red

D no color applied

💡 Hint

Check which container queries match 40rem width and which style applies last.

At 40rem, the min-width: 30rem query applies, setting color to green. The 50rem query does not apply, so red is ignored.

❓ selector

advanced

Which selector correctly targets elements inside a container query?

In Sass, which selector inside a container query will style only direct child

elements of the container?

A p { font-weight: bold; }

B & p { font-weight: bold; }

C & > p { font-weight: bold; }

D > p { font-weight: bold; }

💡 Hint

Remember how Sass uses & to refer to the parent selector.

The & symbol in Sass refers to the parent selector. Using & > p targets direct child <p> elements.

❓ accessibility

expert

How to ensure container queries do not harm accessibility?

Which practice helps maintain accessibility when using container queries for styling?

A Use container queries to hide important content when container is small.

B Ensure color changes meet contrast standards and do not rely solely on color to convey information.

C Apply container queries only to decorative elements without text.

D Avoid using container queries on interactive elements.

💡 Hint

Think about users with vision impairments and how styles affect readability.

Accessibility requires good contrast and not relying only on color changes to communicate meaning, even when using container queries.

Practice

1. What is the main purpose of using @container in Sass?

easy

A. To reset all container styles

B. To create animations for containers

C. To define variables inside containers

D. To apply styles based on the size of an element's container

Solution

1. Step 1: Understand container queries

   Container queries allow styling elements depending on their container's size, not the viewport.

2. Step 2: Role of @container in Sass

   The @container rule in Sass is used to write container queries clearly and apply styles conditionally based on container size.

3. Final Answer:

   To apply styles based on the size of an element's container -> Option D

4. Quick Check:

   Container queries = style by container size [OK]

Hint: Remember: @container styles depend on container size, not viewport [OK]

Common Mistakes:

• Confusing container queries with media queries
• Thinking @container creates animations
• Using @container to define variables

2. Which CSS property must be set on a container element to enable container queries in Sass?

easy

A. container-type

B. container-size

C. container-query

D. container-style

Solution

1. Step 1: Identify container query activation property

   To use container queries, the container must declare container-type to enable size-based queries.

2. Step 2: Verify other options

   container-size, container-query, and container-style are not valid CSS properties for this purpose.

3. Final Answer:

   container-type -> Option A

4. Quick Check:

   Enable container queries = container-type [OK]

Hint: Set container-type to activate container queries on an element [OK]

Common Mistakes:

• Using non-existent properties like container-query
• Confusing container-type with container-size
• Forgetting to set container-type on the container

3. Given the Sass code below, what background color will the .box have if its container width is 500px?

@container (min-width: 600px) {
  .box {
    background-color: blue;
  }
}
.box {
  background-color: red;
}

medium

A. Blue

B. Red

C. No background color

D. Green

Solution

1. Step 1: Understand the container query condition

   The container query applies styles only if the container's width is at least 600px.

2. Step 2: Check container width against condition

   The container width is 500px, which is less than 600px, so the container query block does not apply.

3. Step 3: Determine fallback style

   The .box outside the container query has background-color: red;, so this style applies.

4. Final Answer:

   Red -> Option B

5. Quick Check:

   Container width 500px < 600px = red background [OK]

Hint: Check container width against min-width condition to pick color [OK]

Common Mistakes:

• Assuming container query applies regardless of container size
• Confusing container width with viewport width
• Ignoring fallback styles outside @container

4. Identify the error in the following Sass container query code:

@container (max-width 400px) {
  .card {
    padding: 1rem;
  }
}

medium

A. Container queries cannot use max-width

B. Incorrect selector inside @container

C. Missing colon after max-width

D. Padding value should be in px, not rem

Solution

1. Step 1: Check container query syntax

   The condition inside @container must have a colon after the property name, e.g., max-width: 400px.

2. Step 2: Verify other options

   The selector .card is valid, padding in rem is allowed, and max-width is a valid container query condition.

3. Final Answer:

   Missing colon after max-width -> Option C

4. Quick Check:

   Container query conditions need colons [OK]

Hint: Always use colon after property in container query conditions [OK]

Common Mistakes:

• Omitting colon in container query conditions
• Thinking max-width is invalid in container queries
• Confusing units for padding

5. You want to style a .card component differently when its container is narrower than 300px or wider than 700px using Sass container queries. Which of the following is the correct way to write this?

hard

A. @container (max-width: 300px), (min-width: 700px) { .card { font-size: 1.2rem; } }

B. @container (max-width: 300px) and (min-width: 700px) { .card { font-size: 1.2rem; } }

C. @container (max-width 300px), (min-width 700px) { .card { font-size: 1.2rem; } }

D. @container (width < 300px), (width > 700px) { .card { font-size: 1.2rem; } }

Solution

1. Step 1: Understand container query syntax for multiple conditions

   Multiple conditions separated by commas mean OR logic. Use colons after properties.

2. Step 2: Analyze each option

   @container (max-width: 300px), (min-width: 700px) { .card { font-size: 1.2rem; } } correctly uses commas and colons. @container (max-width: 300px) and (min-width: 700px) { .card { font-size: 1.2rem; } } uses AND which requires both conditions simultaneously (impossible here). @container (max-width 300px), (min-width 700px) { .card { font-size: 1.2rem; } } misses colons. @container (width < 300px), (width > 700px) { .card { font-size: 1.2rem; } } uses invalid syntax with < and >.

3. Final Answer:

   @container (max-width: 300px), (min-width: 700px) { .card { font-size: 1.2rem; } } -> Option A

4. Quick Check:

   Use commas for OR, colons after properties [OK]

Hint: Use commas for OR conditions and colons after properties [OK]

Common Mistakes:

• Using 'and' instead of commas for OR conditions
• Omitting colons in conditions
• Using invalid operators like < or > in container queries