Two springs, stated — and the flat line danger gets instead.

Why it feels right

• The drawer is stiffer and better damped than the toast. Furniture settles with authority; news may carry one visible degree of bounce. Both springs are stated as constants and pinned by the suite.
• While the drawer is open the background is inert — unreachable by pointer, keyboard, and screen reader. A scrim without inert is theater: it dims the page and leaves every trap in it armed.
• The destructive confirm mounts with no motion at all. Danger should not bounce; a spring on a delete reads as charm, and charm is the wrong voice for consequence.
• Toasts cap at three, first in first out. News that has queued behind three newer items is no longer news — a stack that grows without limit is a log wearing a toast's clothes.

Source

/* Two springs, stated and pinned. The drawer is stiffer and better
   damped than the toast: furniture should settle with authority, while
   a toast may carry one visible degree of bounce because it is news. */
export const SPRINGS = {
  drawer: { stiffness: 380, damping: 34 },
  toast: { stiffness: 300, damping: 26 },
} as const;

export type Toast = { id: string; label: string };

export const MAX_VISIBLE = 3;

/* Three toasts, first in first out. A fourth arrival retires the
   oldest: news that has queued behind three newer items is no longer
   news, and a stack that grows without limit is a log, not a toast. */
export function toastQueue(queue: Toast[], next: Toast): Toast[] {
  return [...queue, next].slice(-MAX_VISIBLE);
}