To make an image slide in and stay in place after the animation finishes, you should use position: absolute to position it, left: 0 to ensure it starts from the left edge, animation-fill-mode: forwards to maintain the final state after the animation, and animation-timing-function: ease-in-out to control the animation timing for a smooth effect.

The property commonly used to control the speed curve of a transition effect in CSS is transition-timing-function. This property allows you to specify how the intermediate property values are calculated over the duration of the transition, giving you control over the timing and pace of the transition.

To create a smooth heartbeat animation that makes an icon grow and shrink, you should use the scale transformation with CSS animations. This allows you to scale an element up and down smoothly, ensuring it runs seamlessly in both directions.

The CSS pseudo-class :not() is used to select elements that do not match a specific criteria. It is used to exclude elements that would typically be selected by a CSS selector. For example, :not(.classname) selects all elements that do not have the specified class.

The CSS rule "ul > li" specifically targets only the direct child li elements of a ul element. It will not target li elements that are nested further within the hierarchy of the HTML structure.

The CSS rule "ul + ul" is a sibling combinator that targets an unordered list that immediately follows another unordered list in the HTML structure. This is used to style a specific occurrence of an unordered list in relation to another.

To ensure that an element remains in the normal document flow and doesn't overlap floated siblings, you should use the clear property with a value other than none. This property specifies which side of an element other floating elements are not allowed.

To create a blur effect on an image using CSS, you can use the filter property with the blur function. For example, filter: blur(5px); would apply a blur effect to the image, where "5px" represents the level of blurriness. This can be adjusted to control the blur intensity.

Autoprefixing tools, like Autoprefixer, analyze CSS and add or remove vendor prefixes to ensure compatibility across different browsers. They use data from browser user agents (e.g., Chrome, Firefox) to determine which prefixes are required for specific CSS properties.

When you want to generate multiple class or ID variations in SASS, you would typically use placeholder selectors, also known as %placeholders. These selectors allow you to define styles that can be included in other selectors using the @extend directive, promoting reusability and ensuring cleaner CSS output.