The basic syntax structure of CSS

CSS is a language used to describe the styling of HTML or XML documents, controlling the appearance and layout of page elements through selectors and declaration blocks. Selectors include element selectors, class selectors, ID selectors, attribute selectors, and pseudo-class selectors. Declaration blocks are enclosed in curly braces and consist of properties and values. CSS supports various values and units, such as length units, color values, and function values. Selectors can be combined, and CSS rules follow specificity and inheritance. The box model is a fundamental concept for layout, with layout properties including display, position, and float. Responsive design uses media queries. CSS variables allow storing and reusing values. Pseudo-elements style specific parts of elements. Transitions and animations enable dynamic effects. Modern CSS features include Grid layout, Flexbox layout, and custom filters.

The development history of CSS

The development of CSS began in 1996 with CSS1, which provided basic styling controls like fonts, colors, and text. CSS2, introduced in 1998, brought groundbreaking features such as positioning mechanisms and media queries. CSS3 adopted a modular design, enhancing selectors and adding modern features like rounded corners, shadows, and animations. Flexbox and Grid layouts revolutionized page composition. Modern CSS now includes emerging technologies like variables, container queries, and nested syntax. In the future, CSS will leverage the Houdini project to enable even greater extensibility, allowing developers to create custom CSS properties and layout logic, driving continuous innovation in web design.

The definition and role of CSS

CSS is a stylesheet language used to control the visual presentation and layout of web pages, achieving the separation of content and styles. It defines style rules through selectors and declaration blocks and features cascading properties. CSS supports various layout methods, including float layouts, Flexbox, and Grid layouts, as well as responsive design through media queries to adapt to different devices. The CSS selector system includes basic selectors, combinators, pseudo-classes, and pseudo-elements. The box model consists of content, padding, borders, and margins. CSS also supports animations and transitions, including keyframe animations and transition effects. Modern CSS development uses preprocessors like Sass and custom properties for variable management. CSS modularity is widely applied in front-end frameworks, while performance optimization involves selector efficiency and avoiding reflows and repaints. CSS also focuses on accessibility, providing screen-reader-friendly styles. Future CSS will support new features like container queries and nested syntax.

Background positioning and repetition control

CSS background positioning and repetition control are core techniques for handling element background images. The `background-position` property determines the starting position of the background image, supporting keyword, percentage, and absolute unit positioning, with percentage positioning having special calculation methods. Multiple background layers can be independently positioned. `background-repeat` controls repetition behavior, including basic values and CSS3's advanced control methods. When combined with `background-size`, it can produce rich visual effects. Practical applications include stripe background implementation, sprite optimization, and parallax scrolling. Responsive design requires special attention to mobile adaptation. Performance optimization points include avoiding meaningless repetition and using CSS gradients instead of images. Browser compatibility requires fallback solutions. Creative layouts can combine positioning and repetition to achieve complex patterns. These techniques, when used in combination, enable sophisticated visual effects while optimizing resource usage.

Tips for using background images

CSS background images are implemented via the `background-image` property, supporting multiple path formats and multi-background layering. The `background-repeat` property controls tiling methods, while `background-position` allows precise adjustments using pixels, percentages, or keyword positioning. `background-size` adjusts dimensions, commonly using `cover` and `contain` values. `background-attachment` controls scrolling behavior, enabling parallax effects. `background-clip` defines the painting area, supporting text-clipping effects. `background-blend-mode` achieves blend modes. For optimization, it's recommended to choose appropriate image formats, replace simple patterns with CSS gradients, and use lazy loading. Responsive design adapts to different devices via media queries and `image-set`. Advanced techniques include creating CSS patterns, dynamic gradients, and dynamically modifying backgrounds with CSS variables. Accessibility considerations include providing fallback background colors, high-contrast handling, and adding ARIA attributes for content background images to enhance the user experience.

Multiple ways to set background colors

CSS background color settings are diverse and flexible, including basic color values such as predefined names, hexadecimal, RGB, RGBA, HSL, HSLA, as well as gradient effects like linear gradients and radial gradients. Background images can also be combined with colors, and multiple background layers can be used to achieve complex effects. Dynamic backgrounds can be controlled via CSS variables and JavaScript. Background colors can be inherited or overridden. Special effects include `currentColor`, transparent backgrounds, and responsive designs achieved through media queries. Performance considerations involve how different color formats affect rendering speed, and browser compatibility requires handling legacy support. Accessibility demands sufficient contrast. Background colors can have animation effects, and blend modes can create unique visuals. Background clipping controls display boundaries, and precise positioning manages background images. Pseudo-elements can also set backgrounds, and understanding stacking order is crucial for multiple backgrounds.

Usage of font icons

Font icons are a technical solution that presents icons in the form of fonts, offering advantages such as vector scaling, color control, and smaller file size compared to traditional images. Common libraries include Font Awesome and Material Icons. Essentially, they are special characters implemented through Unicode private area encoding and can be styled via CSS. They can be introduced via CDN or local files. Basic usage methods include class name and Unicode approaches, with CSS allowing adjustments to size, color, and adding effects. Advanced techniques include icon stacking and custom icons. Performance optimization recommendations include on-demand loading and preloading. Common issues like flickering and vertical alignment have solutions. In responsive design, they can be combined with media queries. Compared to SVG icons, each has its own strengths. Modern frameworks like React and Vue also have dedicated usage methods.

Control of text layout direction

CSS text layout direction control involves several key properties for precise management of text flow, including left-to-right, right-to-left, and vertical arrangements. Basic properties include `direction` for controlling text alignment and element flow direction, `writing-mode` for determining whether text is arranged horizontally or vertically, and `text-orientation` for adjusting character orientation in vertical layouts. `unicode-bidi` handles mixed-direction text. Practical applications include vertical navigation menus and multilingual website layouts. Advanced techniques involve direction-sensitive layouts, combining Flexbox and Grid with direction properties, and animation effects. Browser compatibility requires fallback solutions, while performance optimization suggests avoiding frequent direction changes and using `will-change` and CSS Containment. For internationalization, pair with HTML's `lang` attribute and font selection. Debugging can be done using developer tools to inspect computed styles. Common issue resolutions cover punctuation placement, digit direction, and mixed-text alignment.

First line indentation and letter spacing

In web design, first-line indentation and letter spacing are techniques used to control text layout. First-line indentation is achieved using the `text-indent` property, with common units including px, em, and percentage. The em unit, based on font size, better aligns with typographic needs, and negative values can create hanging indent effects. Letter spacing is controlled by the `letter-spacing` property, where positive values increase spacing and negative values reduce it. Large headings often use wider spacing to enhance readability, while small text may benefit from slightly increased spacing. All-caps text requires additional spacing. These techniques can be combined for unique layouts. Browser compatibility should be noted—older versions of IE have poor support for percentage-based indentation, and mobile devices may require fine-tuned minimal spacing. Performance-wise, frequent changes to letter spacing may trigger reflows, while first-line indentation has a smaller performance impact, though heavy usage can increase computational load.

Text overflow and ellipsis display

Text overflow is a common layout issue in front-end development. CSS provides various solutions, with using ellipsis to represent truncated text being the most common approach. Single-line text ellipsis requires four conditions: the element must have a defined width, line breaks must be disabled, overflow content must be hidden, and an ellipsis must be displayed. Multi-line text truncation is implemented based on WebKit's private properties, requiring the setting of the number of displayed lines and vertical orientation. In responsive design, text truncation can be handled dynamically. Table cells require special treatment, and pseudo-elements can create richer truncation effects. Right-to-left text needs specific handling. JavaScript enables more precise control. When using text truncation, accessibility issues must be considered, and excessive use may impact rendering performance. Browser-specific compatibility solutions are needed for different browsers. Practical applications include navigation menus, card components, data tables, etc. Advanced techniques include combining Flexbox layouts, dynamically adjusting truncation points, and displaying full text on hover.