Workshop › Tetris-style Blocks › Step 9 of 32

Does it fit inside the well?

What we are doing

Every rule of the game comes down to one question: does this shape fit at this place? First part: every filled cell must be inside the well's sides and above its floor.

```js
function fits(shape, x, y) {
  for (let r = 0; r < shape.length; r++) {
    for (let c = 0; c < shape[r].length; c++) {
      if (!shape[r][c]) continue
      const col = x + c
      const row = y + r
      if (col < 0 || col >= COLS || row >= ROWS) return false
    }
  }
  return true
}
```

What it means

fits takes the shape and a place as parameters, so it can answer "what if?" questions before anything moves.
Two loops visit every cell of the matrix; continue skips the empty ones: empty cells never collide.
col and row are where the cell would be in the well. Left of the wall, right of it or under the floor: it does not fit, and return false ends the function at once.
If every cell passed, return true.

Your turn

Write fits under the let piece line, after an empty line.

Skills: Collision detection, Functions

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