Describe the precise technique for creating a truly responsive layout where elements not only resize but also intelligently rearrange their internal spacing and alignment based on available screen real estate, even when elements are dynamically added or removed.

Creating a truly responsive layout involves a combination of modern CSS features that allow elements to adapt their size, spacing, and arrangement based on the viewport or container size, and to react to dynamic content changes. The core technique relies on Flexbox and CSS Grid, along with media queries and careful use of units and intrinsic sizing. Flexbox is a one-dimensional layout model, meaning it primarily deals with layout in a single direction – either a row or a column. It excels at distributing space along that axis and aligning items within it. CSS Grid is a two-dimensional layout model, allowing simultaneous control over rows and columns, making it ideal for complex overall page layouts. To achieve intelligent rearrangement, we first establish a flexible container. For example, a `div` with `display: flex;` becomes a flex container. Its direct children become flex items. By default, flex items try to fit onto one line. Using `flex-wrap: wrap;` on the flex container tells its items to wrap onto multiple lines if they overflow the container's width. This is a fundamental mechanism for rearranging elements. For more sophisticated grid-based layouts, `display: grid;` is used on a container. We define columns and rows using properties like `grid-template-columns` and `grid-template-rows`. For instance, `grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));` tells the browser to create as many columns as can fit, with each column being at least 200 pixels wide and growing to fill available space (`1fr` means one fraction of the available space). The `auto-fit` keyword ensures that when there isn't enough space for a full row of minimum-width items, the columns collapse and stretch to fill the remaining space, effectively rearranging the layout. Spacing is managed using `gap` (for both Flexbox and Grid) or `justify-content` and `align-items` within Flexbox. `gap` provides consistent spacing between grid or flex items. `justify-content` aligns items along the main axis (horizontally in a row, vertically in a column), with values like `space-between` distributing items with equal space between them, `space-around` with equal space around them, and `center` grouping them in the middle. `align-items` aligns items along the cross axis. Alignment within individual items is controlled by `align-self` on flex items or `align-self` and `justify-self` on grid items. For dynamic content addition or removal, these layout models inherently handle resizing. When an item is added to a flex or grid container, it automatically occupies available space according to the container's rules. When an item is removed, the remaining items readjust their positions and spacing. This is because the layout is calculated in real-time by the browser. Media queries are crucial for defining different layout behaviors at specific screen sizes. A media query like `@media (max-width: 768px) { ... }` applies styles only when the viewport width is 768 pixels or less. Within media queries, we can change `flex-direction` (e.g., from `row` to `column`), adjust `grid-template-columns`, modify `gap` values, or alter alignment properties to create distinct layouts for different devices. Intrinsic sizing, where elements define their own size based on their content, also plays a role. Using relative units like percentages (`%`) or viewport units (`vw`, `vh`) for element widths and heights allows them to scale proportionally. However, relying solely on percentages can sometimes lead to undesirable shrinking. Combining `minmax()` with `fr` units in Grid, or setting `min-width` and `max-width` on flex items, provides better control, ensuring elements don't become too small or too large. For example, setting `min-width: 150px;` on a flex item prevents it from shrinking below that size, forcing a wrap if necessary. The key is to design the layout with flexibility in mind from the start, using these CSS tools to instruct the browser on how to adapt rather than hardcoding fixed sizes and positions.