Learning Goals 3 min
By the end of this lesson you will be able to:
- Name the four edges of the Stage: x =
-240, x =240, y =-180, y =180. - Read any sprite’s x and y straight from the Sprite Properties bar.
- Drag the cat to a named spot in the garden and say its coordinate pair out loud.
Warm-Up 7 min
Your cat walks exact distances and turns proper corners. But you still cannot tell it to go to a particular place — only how far to walk from wherever it happens to be. Today you fix that, starting with the map.
Quick-fire puzzle
Priya set Direction to 90 and started the cat at x = -100, y = 50. Where did it end up?
when flag clicked
move (200) steps
Reveal the answer
The cat ended at x = 100, y = 50. The x climbed from −100 to 100 because the cat travelled 200 to the right. The y did not budge, because nothing moved it up or down.
That is the big idea: a move changes x, or y, or both, depending purely on which way the cat faces. Today you learn what those two numbers actually mean.
New Concept — the Stage’s coordinate map 15 min
The Stage is a grid, like the squared paper in your maths book — except the centre sits exactly in the middle rather than in a corner. Every spot carries two numbers: an x for how far left or right, and a y for how far up or down.
The two numbers we read today
| Reading | Where to find it | What it tells you |
|---|---|---|
| x position | Sprite Properties, the x box | How far left or right of centre. Runs from −240 to 240. |
| y position | Sprite Properties, the y box | How far above or below centre. Runs from −180 to 180. |
Notice these are not blocks. They are readouts — the Sprite Properties bar shows them constantly, and they update the instant anything moves.
Writing a coordinate
Always write x first, then y, inside brackets with a comma between:
(0, 0)— dead centre.(240, 0)— the right edge, halfway up.(0, 180)— the top edge, halfway across.(-100, 50)— a little left of centre, a little above it.(-240, -180)— the bottom-left corner.
Drag and read
The fastest way to feel this is with your mouse. Click and hold the cat on the Stage, drag it slowly, and keep your eye on the x and y boxes. Drag left and only x changes. Drag up and only y changes. Drag diagonally and both move at once.
Why negative is not “bad”
A negative number here means nothing more than a direction — left of centre for x, below centre for y. A cat at (-200, -160) is not broken, it is just sitting in the bottom-left of the garden.
Why it matters
Every Scratch game runs on coordinates. A target in the top-right, a score in the top-left, a player starting at the bottom. Coordinates are the floor plan of your project — and from next lesson, the address you hand to a block.
Worked Example — map the garden 15 min
No new blocks today. Instead you tour the garden with your mouse and learn to read where the cat is standing.
Step 1 — Send the cat home
Select the cat and type x = 0, y = 0, Direction = 90. It sits dead centre, where the two dashed lines cross.
Step 2 — Watch a move change one number
Build the two-block stack below and click the flag once.
when flag clicked
move (100) steps
The x box goes from 0 to 100. The y box does not move at all — the cat travelled sideways, so only its sideways number changed.
Step 3 — Drag to the top-left
Put the blocks down and use your mouse. Drag the cat up and to the left, near the butterfly. Read the boxes: x is a large negative number, y is a large positive one. Write down what you see, something like (−162, 104).
Step 4 — Drag to the bottom-right
Now drag down and right, toward the frog. The x has turned positive and the y negative — roughly (158, −118). Two numbers, and between them they pin down exactly one spot in the garden.
Step 5 — Drag straight up
From wherever you are, drag the cat directly upward, keeping it in a vertical line. Only y climbs. The x stays where it was. This is the clearest way to see that the two numbers are independent.
Step 6 — Find your way home by eye
Drag slowly toward the middle and watch both numbers shrink. When both read 0, or very nearly, let go. You have just navigated by coordinates.
What changed: you added no blocks at all, and yet the Stage went from a blank rectangle to a map you can give directions on. That is what makes the next lesson possible.
Your tour log
Write the four landmark coordinates into your notebook. In Lesson 10 you will hand exactly those numbers to a block and watch the cat arrive without a single drag.
Try It Yourself — three map drills 12 min
Goal: Predict one number. Type x = 120, y = 0 into Sprite Properties, then run the stack and check whether the x box matches your prediction.
when flag clicked
move (50) steps
Think: 120 + 50 = 170. And the y box never moved, because nothing sent the cat up or down.
Goal: Park the cat in each quarter of the garden, one at a time, using only your mouse. For each one, write down the pair of numbers and whether each is positive or negative.
Think: the two dashed lines split the garden into four. Which quarter you are in is decided entirely by whether each number is above or below zero.
Mini-mission: predict the landing. Point the cat downward instead of right, then work out — on paper, before you click — exactly which boxes will change and by how much.
It works if: you write both predicted numbers in your notebook before clicking, and both turn out right. Set x = -100, y = 0, Direction = 180 first.
when flag clicked
move (80) steps
Think: which of the two boxes can a downward move possibly change? And does the number go up or down when a sprite travels toward the bottom of the Stage?
Mini-Challenge — name that corner 5 min
“The four-corner tour”
Park the cat in each of the four corners of the garden in turn, using only the Sprite Properties boxes — no blocks. Write down the pair of numbers you typed each time.
It works if:
- The cat visits all four corners, one at a time.
- You write a pair of numbers for each corner before typing them in.
- Every prediction turns out to put the cat exactly where you expected.
- You can say which corner has both numbers at their smallest.
Reveal the four answers (teacher)
- Top-left:
(-240, 180)— x at its lowest, y at its highest. - Top-right:
(240, 180)— both at their highest. - Bottom-left:
(-240, -180)— both at their lowest. - Bottom-right:
(240, -180)— x highest, y lowest.
A common slip is swapping the pair for the top-left and bottom-left corners — worth asking which of the two numbers actually changed between them.
Recap 2 min
The Stage is a grid and every spot has two numbers — x for left and right, y for up and down. The centre is (0, 0) and the corners sit at ±240 and ±180. You can read both numbers in the Sprite Properties bar, or type them in to park a sprite anywhere you like. Next lesson a block does the same job in one snap.
- Coordinate
- A pair of numbers (x, y) naming exactly one spot on the Stage.
- x position
- The left-and-right number, from −240 at the left edge to 240 at the right.
- y position
- The up-and-down number, from −180 at the bottom to 180 at the top.
- Origin
- The dead centre of the Stage, always (0, 0).
Homework 1 min
The five-stop map. Visit five spots on the Stage by typing coordinates into Sprite Properties, writing each pair down as you go.
- Select the cat, then type each pair into Sprite Properties in turn:
- Stop 1 — the centre: x =
0, y =0. - Stop 2 — the top edge: x =
0, y =180. - Stop 3 — the right edge: x =
240, y =0. - Stop 4 — anywhere in the bottom-left quarter, so both numbers are negative.
- Stop 5 — anywhere in the top-right quarter, so both numbers are positive.
- Stop 1 — the centre: x =
- Screenshot the Stage at stops 4 and 5.
Bring back next class:
- Both screenshots.
- All five pairs of coordinates written out.
- Your answer to: “Which corner of the Stage has the most negative x and the most negative y?”
Heads up for next class: SCR-L01-10 introduces go to x: (0) y: (0). The cat will jump straight to any address in a single block — no dragging, no typing.