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X and Y Coordinates

The scratch “stage” is a Cartesian (x-y) plane, with (0,0) in the centre.

The “x” number is the horizontal position, with positive numbers being “to the right of the middle” and negative numbers being “to the left of the middle”.  The “y” number is the vertical position, with negative numbers being “below the middle” and positive numbers being “above the middle”.

Objectives

  • Introduce the Scratch “stage” and axis orientations.

Materials

  • Per Student:
    1 computer  (**at least one computer per two students**)

  • Per Class: 
    Computer with projector or SMART board.

Key Questions

  • How would you get the sprite to move into the upper right hand corner? (Go to x:189 y:125, or other large positive numbers)
  • How would you get the sprite to move into the lower left hand corner? (Go to x:-189 y:-125, or other large negative numbers)

What To Do

Preparation:

Ensure that all the computers work, and are connected to the internet.
Set up the instructor computer and projector or SMART board.  Log in to the Scratch website.

Activity:

Instructor:

  1. On the screen or SMART Board, create a new scratch project and select the Motion tab. Change the backdrop to “xy-grid” to make the following steps even more obvious.
  2. Show students that the position of the sprite is noted in the lower right hand corner of the stage window.  Move the sprite around to show how the numbers change.
  3. If students are unfamiliar with x and y coordinates, explain that the “x” number is the horizontal position, with positive numbers being “to the right of the middle” and negative numbers being “to the left of the middle”.  The “y” number is the vertical position, with negative numbers being “below the middle” and positive numbers being “above the middle”.
  4. Show students the “go to” block by dragging it into the logic window.
  5. Ask: How would you get the sprite to move into the upper right hand corner? How would you get the sprite to move into the lower left hand corner?
  6. Students should experiment with the “go to” block as they answer.
  7. Demonstrate the effect of the “move” and “turn” blocks.

Students:

  1. Explore the “move”, “turn” and “go to” blocks.
  2. Create your own logic that moves a sprite in a square.

Modification: Use one or more of the pen blocks to cause your sprite to draw a square

Extensions