Catch the Roti Canai

Learning Goals 3 min

By the end of this lesson you will be able to:

1. Assemble a complete game from a title, a scoring loop and an ending.
2. Test a project the way a stranger would, and fix what that finds.
3. Save, name and share a finished Scratch project with instructions.

Warm-Up 7 min

Everything in today’s game already exists in your project. What is missing is the frame around it — the part that tells a player what to do and when they are finished.

Quick-fire puzzle

Hand your project to the person next to you without saying anything. Watch what they do first.

New Concept — the shape of a finished game 15 min

A finished game has three parts, and only one of them is the game. You have spent three lessons on the middle. Today you build the two ends, which together take about ten minutes.

The rule that ties it together

The flag script must put the project into exactly the same state every time, no matter what the previous run left behind. That covers the score, the roti’s position, its size, whether it is showing, and which readouts are on screen.

You have met this idea in every arc of this level. It is the last time it will be new, because from now on you will simply do it.

Blocks you will use today

Why it matters

Finishing is a skill of its own, and it is rarer than starting. Plenty of people can build a catch loop. Far fewer wrap it up so a stranger can pick it up and play.

Worked Example — finish the game 15 min

Open your project from last lesson. You are adding the two ends and then testing hard.

Step 1 — The title, on the cat

Select the cat. This script tells the player what to do before anything else happens.

when flag clicked
hide variable [score v]
say [Click the roti! Space to stop.] for (3) seconds
set [score v] to (0)
show variable [score v]
say [Go!] for (1) seconds
        

Step 2 — The reset, on the roti

Select the roti. The flag has to undo everything a previous game did to it.

when flag clicked
hide
set size to (100) %
go to x: (0) y: (0)
wait (4) seconds
show
        

Step 3 — The catch loop, unchanged

This is last lesson’s script. It does not need touching, which is a good sign.

when this sprite clicked
start sound [Pop v]
change [score v] by (1)
change size by (20)
wait (0.1) seconds
change size by (-20)
go to [random position v]
        

Step 4 — The ending, on the roti

Space ends the round. The roti has to disappear, or the player carries on scoring during their own victory.

when [space v] key pressed
stop [other scripts in sprite v]
hide
        

Step 5 — The result, on the cat

The cat announces the score. The variable reporter goes straight into the say block.

when [space v] key pressed
say (score) for (3) seconds
say [Green flag to play again!] for (3) seconds
        

Step 6 — Test it like a stranger

Run the whole thing three times in a row without stopping to fix anything. Write down every single thing that looks wrong, then fix them afterwards.

Testing and fixing at the same time is how bugs get missed. Separate the two and you find more.

Step 7 — Name it and save it

Give the project a real title — Catch the Roti Canai — and fill in the instructions box: what to click, how to score, how to stop. Then save.

What changed: you no longer have a project you have to explain. You have a game someone can play without you in the room.

The full script list (your reference)

Five scripts across two sprites. Every one of them is under eight blocks.

Try It Yourself — three small builds 12 min

when [space v] key pressed
say [Wah, so many roti!] for (2) seconds
say (score) for (3) seconds
          

when this sprite clicked
change [score v] by (1)
change size by (-4)
go to [random position v]
          

Mini-Challenge — the stranger test 5 min

“Hand it over and say nothing”

Swap seats with someone who has not seen your game. Watch them play without helping, without explaining and without touching the mouse. Write down what confuses them.

It works if:

• You watch someone play without saying a word.
• You write down at least two things that confused them.
• You fix both, then have a second person try it.
• The second person needs less help than the first.

Recap 2 min

A finished game is a start, a middle and an end, and only the middle is the game. The flag script has to return the whole project to a known state, whatever the last run left behind — you have now met that rule in six arcs. An ending has to stop things as well as announce them, or the player keeps scoring after they have won. And handing your project to a stranger finds more bugs in three minutes than an hour of testing it yourself.

Ship it

Finishing and releasing a project rather than leaving it nearly done.

Reset script

The flag script that returns every sprite and variable to its starting state.

Stranger test

Watching someone play with no help, to find what your game fails to explain.

Instructions

The notes on a shared project telling a player what to do.

Homework 1 min

One more player. Your game has been tested by a classmate. Now test it on someone who has never used Scratch.

1. Ask a family member to play your shared game with no explanation from you.
2. Watch what they do in the first ten seconds and write it down.
3. Note down every question they ask you.
4. Make one change to the game that would have answered their first question.

Bring back next class:

• Your list of their questions, and the one change you made.
• Your answer to: “What did you have to explain out loud, and where should that have been written into the game instead?”

Heads up for next class: SCR-L01-44 is a build lesson — Cat Chase, a game where the target does not wait to be clicked.