Future CSS features replacing SASS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding CSS Nesting vs SASS Nesting

Which of the following CSS snippets correctly uses the new CSS nesting feature to replicate the SASS nesting below?

.menu {
  color: black;
  .item {
    color: red;
  }
}

A

.menu {
  color: black;
  & .item {
    color: red;
  }
}

B

.menu {
  color: black;
  .item {
    color: red;
  }
}

C

.menu {
  color: black;
  & > .item {
    color: red;
  }
}

D

.menu {
  color: black;
  &.item {
    color: red;
  }
}

💡 Hint

Remember that CSS nesting uses the & symbol to refer to the parent selector.

In CSS nesting, the & symbol represents the parent selector. Option A correctly nests .item inside .menu by using '& .item'. Option A is invalid CSS nesting syntax. Option A uses a child combinator which changes the meaning. Option A concatenates selectors which is incorrect here.

📝 Syntax

intermediate

Using CSS Variables with calc() instead of SASS variables

Given the SASS code below, which CSS code correctly uses CSS custom properties and calc() to achieve the same dynamic spacing?

$base-spacing: 1rem;
.container {
  padding: $base-spacing * 2;
}

A

.container {
  padding: calc(1rem * 2);
}

B

:root {
  --base-spacing: 1rem;
}
.container {
  padding: var(--base-spacing) * 2;
}

C

:root {
  --base-spacing: 1rem;
}
.container {
  padding: calc(var(--base-spacing) * 2);
}

D

.container {
  padding: 2rem;
}

💡 Hint

CSS variables require var() and calc() for arithmetic.

Option C correctly defines a CSS variable and uses calc() with var() to multiply the value. Option C is invalid because CSS does not allow direct multiplication without calc(). Option C hardcodes the value but does not use variables. Option C hardcodes the value without variables or calculation.

❓ selector

advanced

Which CSS selector replicates SASS @at-root behavior?

SASS's @at-root allows styles to be placed outside the current nesting. Which CSS selector technique can replicate this behavior in future CSS?

Consider this SASS:

.card {
  &__title {
    @at-root {
      .highlight {
        color: blue;
      }
    }
  }
}

A

.card__title:has(.highlight) {
  color: blue;
}

B

.card__title .highlight {
  color: blue;
}

C

:is(.card__title) :where(.highlight) {
  color: blue;
}

D

.card__title {}
.highlight {
  color: blue;
}

💡 Hint

Think about how to write styles outside the nested selector.

Option D places .highlight outside the nested .card__title, replicating @at-root behavior. Option D nests .highlight inside .card__title, which is different. Options A and C use pseudo-classes that do not replicate @at-root.

❓ layout

advanced

Replacing SASS Mixins with CSS @layer and Custom Properties

SASS mixins allow reusable style blocks. Which CSS feature below best replaces mixins for managing reusable styles with layering and variables?

Choose the CSS code that uses @layer and custom properties to create a reusable button style.

A

@mixin btn-style {
  padding: 1rem;
  background: blue;
  color: white;
}
.btn {
  @include btn-style;
}
.btn-primary {
  background: green;
}

B

@layer buttons {
  .btn {
    padding: var(--btn-padding, 1rem);
    background: var(--btn-bg, blue);
    color: white;
  }
}

.btn-primary {
  --btn-bg: green;
}

C

.btn {
  padding: 1rem;
  background: blue;
  color: white;
}
.btn-primary {
  background: green;
}

D

.btn {
  @apply padding: 1rem; background: blue; color: white;
}
.btn-primary {
  background: green;
}

💡 Hint

Look for CSS features that support layering and variables for reuse.

Option B uses @layer to organize styles and custom properties for flexible reuse, replacing mixins. Option B uses invalid @apply syntax not supported in standard CSS. Option B is SASS code, not CSS. Option B hardcodes styles without reuse or layering.

❓ accessibility

expert

Ensuring Accessibility with Future CSS Features Replacing SASS

When replacing SASS color functions like darken() with CSS custom properties and color-mix(), which option ensures the best accessibility by maintaining sufficient contrast for text on backgrounds?

Assume --primary-color is a blue shade.

A color: color-mix(in srgb, var(--primary-color) 80%, black 20%);

B color: color-mix(in srgb, var(--primary-color) 20%, black 80%);

C color: var(--primary-color);

D color: darken(var(--primary-color), 20%);

💡 Hint

Higher percentage of primary color keeps the color lighter and more readable.

Option A mixes 80% primary color with 20% black, producing a slightly darker color that maintains good contrast. Option A is mostly black, which may be too dark or not match design. Option A uses the original color without adjustment. Option A uses SASS function which is not valid CSS.

Practice

1. Which future CSS feature allows you to store reusable values like colors or sizes directly in CSS without using SASS variables?

easy

A. CSS Modules

B. CSS Custom Properties (variables)

C. CSS Functions

D. CSS Mixins

Solution

1. Step 1: Understand CSS Custom Properties

   CSS Custom Properties let you define variables using the syntax --name: value; inside selectors.

2. Step 2: Compare with SASS variables

   SASS variables are replaced by CSS Custom Properties which work natively in browsers and can be reused.

3. Final Answer:

   CSS Custom Properties (variables) -> Option B

4. Quick Check:

   Variables in CSS = CSS Custom Properties [OK]

Hint: Remember CSS variables start with double dashes -- [OK]

Common Mistakes:

• Confusing CSS Mixins with variables
• Thinking CSS Functions are variables
• Assuming CSS Modules are variables

2. Which of the following is the correct syntax for nesting selectors using future CSS features (without SASS)?

easy

A. nav { ul { list-style: none; } }

B. nav > ul { list-style: none; }

C. nav { & ul { list-style: none; } }

D. nav ul { list-style: none; }

Solution

1. Step 1: Understand future CSS nesting syntax

   Future CSS uses the & nesting selector to nest selectors, e.g., nav { & ul { list-style: none; } }.

2. Step 2: Compare with SASS nesting

   SASS allows direct nesting like nav { ul { ... } }, but future CSS requires & or pseudo-classes like :is() or :where().

3. Final Answer:

   nav { & ul { list-style: none; } } -> Option C

4. Quick Check:

   Nesting in CSS uses & or :is()/:where() [OK]

Hint: Future CSS nesting uses & nesting selector [OK]

Common Mistakes:

• Using SASS style nesting directly (without &)
• Confusing child selector > with nesting
• Using descendant selector without nesting

3. What will be the computed background color of the <div> in this CSS using future CSS variables?

:root { --main-color: coral; } div { background-color: var(--main-color); }

medium

A. var(--main-color)

B. transparent

C. black

D. coral

Solution

1. Step 1: Identify the variable definition

   The variable --main-color is set to coral in the :root selector, making it global.

2. Step 2: Apply the variable in div

   The div uses background-color: var(--main-color); which fetches the value coral.

3. Final Answer:

   coral -> Option D

4. Quick Check:

   CSS variable value applied = coral [OK]

Hint: var() fetches the value of CSS custom properties [OK]

Common Mistakes:

• Thinking var() outputs the variable name
• Assuming default color if variable is defined
• Confusing transparent with variable usage

4. Identify the error in this future CSS code snippet that tries to use nesting:

section { article { padding: 1rem; } }

medium

A. Nesting must use & or :is() or :where()

B. The ampersand (&) is not supported in future CSS nesting

C. Incorrect property name 'padding'

D. Missing semicolon after padding value

Solution

1. Step 1: Check nesting syntax in future CSS

   Future CSS requires nested selectors to start with & or pseudo-classes like :is() or :where(). Plain article is invalid.

2. Step 2: Identify correct nesting method

   Correct would be section { & article { padding: 1rem; } } or using pseudo-classes.

3. Final Answer:

   Nesting must use & or :is() or :where() -> Option A

4. Quick Check:

   Future CSS nesting requires & or pseudo-classes [OK]

Hint: Future CSS nesting requires & or :is()/:where() [OK]

Common Mistakes:

• Using plain selectors without & or pseudo-class
• Ignoring missing semicolon which is correct here
• Confusing property names

5. You want to create a responsive design using future CSS features replacing SASS. Which is the correct way to write a media query that changes font size for screens wider than 600px?

medium

A. @media screen and (min-width: 600px) { body { font-size: 1.2rem; } }

B. @media (min-width: 600px) { body { font-size: 12; } }

C. @media screen (min-width: 600px) { body { font-size: 1.2rem; } }

D. @media (min-width: 600) { body { font-size: 1.2rem; } }

Solution

1. Step 1: Understand media query syntax

   Future CSS uses standard CSS media queries. The correct syntax includes the media type, e.g., screen and (min-width: 600px).

2. Step 2: Check font size units

   Using 1.2rem is better for accessibility and scaling than fixed pixels.

3. Final Answer:

   @media screen and (min-width: 600px) { body { font-size: 1.2rem; } } -> Option A

4. Quick Check:

   Media query with screen and rem units [OK]

Hint: Always include media type and use rem units for fonts [OK]

Common Mistakes:

• Omitting 'and' after media type 'screen'
• Using px instead of rem for font size
• Missing 'px' unit in media query