Snake, with one idea of your own

Build a playable Snake game that runs from `index.html`, and add **exactly one original
mechanic of your own design** on top of it.

## The Snake part (fixed, so every version is comparable)

- A 24×24 grid rendered on a canvas, roughly 720×720 CSS pixels.
- Arrow keys and WASD both steer. The snake cannot reverse directly into itself.
- Eating food grows the snake by one segment and scores a point. New food never appears on the
  snake.
- Hitting a wall or yourself ends the game. A game-over state shows the score and restarts on a
  keypress, fully resetting everything.
- The snake moves on a fixed tick (start around 8 steps per second) that speeds up slowly as it
  grows, with a floor on the tick length.
- Score and high score are visible; the high score persists across reloads via `localStorage`.
- Pause on **P** or **Escape**.

## The twist (yours)

Invent **one** mechanic that changes how the game is played — not a cosmetic effect. It should
be simple enough to explain in a sentence and should create a real decision for the player,
ideally a trade-off. Then:

- Make it work properly, including its interaction with growing, dying and restarting.
- Give it a name.
- Print the name and its one-sentence explanation on the page, under the board, so a player
  knows the rule before they start.

Do not add a second twist. One idea, done well, is the task.

## Requirements

- Everything drawn with canvas or CSS — no images, no network.
- The tick loop must not drift or speed up on faster displays.
- Keys used by the game must not scroll the page.
- Show the controls on the page.

Make it feel good to play: readable at a glance, responsive input, an obvious moment of
feedback when you eat something.