Workshop › Tetris-style Blocks › Step 11 of 32

Try, then move

What we are doing

tryMove(dx, dy) asks fits about the new place first and moves only if the answer is yes. It returns whether it moved.

```js
function tryMove(dx, dy) {
  if (!fits(piece.shape, piece.x + dx, piece.y + dy)) return false
  piece.x += dx
  piece.y += dy
  return true
}
```

What it means

• dx and dy say how many columns right and rows down: left is (-1, 0), down is (0, 1).
• If the piece would not fit at the new place, return false without changing anything.
• Otherwise move it (+= adds) and return true.

Your turn

Write tryMove under fits, after an empty line.

Skills: Collision detection, Functions

← Blocks are in the way Move with the arrows →

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