In CSS, the 'width' property is used to set the width of the content area of an element. It controls the width of the element's content, excluding padding, border, and margin.

To use a custom property in your styles in CSS, you reference it with the @ symbol. Custom properties, also known as CSS variables, are defined using the :root pseudo-class, and their values can be accessed and used in your styles by prefixing the custom property name with the @ symbol.

The inherit value in CSS makes the element inherit the computed value of the property from its parent element. It ensures that the property's value is taken from the parent element, allowing for consistent styling throughout the document.

The @keyframes rule in CSS is used to create animations over a set duration. You define specific animation steps within the @keyframes rule, and then you can apply this animation to elements using the animation property. It allows you to control how an element changes over time.

To blend the background images of an element in CSS, you should use the background-blend-mode property. This property allows you to control how the background images blend with each other and with the element's background color. It offers various blending modes to achieve different visual effects.

The CSS property used to change the text case, such as making text all uppercase, is text-transform. It allows you to control the capitalization of text, including options like uppercase, lowercase, and capitalize. This is especially useful for headings and other text elements where you want to change the case style.

The @keyframes rule in CSS is used to specify the keyframes for CSS animations. Keyframes describe how an animation progresses from the starting state to the ending state. They define the intermediate steps or percentage-based changes in the animation's properties, allowing for smooth and controlled animations.

For setting the "line-height" property to ensure consistent spacing, the recommended unit is typically "em." Using "em" units allows the line height to be relative to the font size, which ensures that the spacing remains consistent even if the text size changes. This is especially useful for creating responsive and accessible web designs.

To create a theme switcher in SASS/SCSS, you can define different color variables and use SASS/SCSS functions to return the appropriate color values based on the selected theme. This allows you to switch themes easily by changing a single variable and ensures consistency across your project.

The default value of the animation-direction property in CSS is normal. When animation-direction is set to normal, the animation plays forward, and then it starts from the beginning when it reaches the end, creating a continuous loop.