Workshop › Tetris-style Blocks › Step 17 of 32

A random piece at the top

What we are doing

Instead of always the T, spawn() puts a copy of a random shape at the top of the well, centred.

```js
let piece

function randomShape() {
  return SHAPES[Math.floor(Math.random() * SHAPES.length)].map((row) => [...row])
}

function spawn() {
  const shape = randomShape()
  piece = { shape, x: Math.floor((COLS - shape.length) / 2), y: 0 }
}

spawn()
requestAnimationFrame(loop)
```

What it means

• Math.random() gives a number from 0 up to (not including) 1; times 7 and rounded down with Math.floor, it is a whole number 0 to 6: a random index into SHAPES.
• (COLS - shape.length) / 2 centres the matrix; Math.floor rounds it down to a whole column.
• { shape, x, y } is short for { shape: shape, ... }.
• spawn() at the bottom makes the first piece.

Your turn

1. Change let piece = ... to just let piece.
2. Above the // Clockwise... comment write randomShape and spawn.
3. At the bottom, write spawn() above requestAnimationFrame(loop).

Skills: Game states

← Falling by itself Land and lock →

All steps

1. The well
2. The board as rows of numbers
3. Draw one cell
4. Draw the whole board
5. The number is the color
6. A piece is a small grid
7. A list of shapes
8. All seven pieces
9. Does it fit inside the well?
10. Blocks are in the way
11. Try, then move
12. Move with the arrows
13. Turn a matrix
14. Turn with Up
15. Wall kicks
16. Falling by itself
17. A random piece at the top
18. Land and lock
19. One function starts a game
20. When the pile reaches the top
21. Game Over on screen
22. Play again
23. Clear full rows
24. Points for lines
25. The side panel
26. Levels
27. Faster every level
28. A fair bag of pieces
29. The next piece
30. Drop it
31. The ghost piece
32. Build it yourself: hold a piece