Lesson 1 of 5 · Hawker Centre

Sequencing: a 45-minute coding lesson

A free 45-minute lesson on sequencing for ages 6–12. Students plan step-by-step instructions to deliver chicken rice in a Singapore hawker centre.

  • 45 minutes
  • Pairs, whole class
  • One device per pair, plus a projector
Open level 1

Learning objectives

By the end of the lesson, students can:

  • Explain that a program is a list of instructions followed in order.
  • Write a sequence of moves and actions to reach a goal.
  • Find and fix a bug when instructions are in the wrong order.

Key words

Program:
A set of instructions for a computer to follow.
Sequence:
Instructions carried out one after another, in order.
Bug:
A mistake in a program that makes it do the wrong thing.
Debugging:
Finding and fixing bugs.

You'll need

  • One laptop, Chromebook or iPad per pair, open to dotcodecampus.com/maze/hawker/1. No accounts or installs.
  • A projector or screen for the demo.
  • Optional: the printable unplugged grid game for the warm-up, and certificates to finish.

Lesson flow

  1. Minutes 0–8

    Unplugged warm-up

    • Ask a volunteer to be the "robot". They may only follow exact instructions: step forward, turn left, turn right.
    • The class directs the robot from the door to a chair. Write each instruction on the board as it is given.
    • Deliberately give one wrong step. Ask: what went wrong, and which line on the board do we change?

  2. Minutes 8–15

    Demo on the projector

    • Open Hawker Centre level 1 on the projector (dotcodecampus.com/maze/hawker/1).
    • Point out the robot, the tray it is holding, and the hungry diner. Ask the class how many squares away the table is.
    • Drag the blocks in as the class calls them out, press Run, and celebrate the stars.

  3. Minutes 15–35

    Paired play: levels 1–6

    • Work in pairs: a "driver" who moves the blocks and a "navigator" who plans the path. Swap at each new level.
    • Encourage pairs to predict what will happen before pressing Run, then check.
    • Level 4 introduces the trolley uncle. Ask stuck pairs to watch him for a while before planning.
    • Pairs who finish can try for three stars on every level to unlock the secret bonus level.

  4. Minutes 35–42

    Class discussion

    • What happened when you tried to serve before picking up the tray? Why?
    • How did you get past the trolley uncle? Did everyone find the same path?
    • Where else do the steps have to be in the right order? (A recipe, brushing your teeth, getting dressed.)

  5. Minutes 42–45

    Exit ticket

    • Write the three blocks, in order, that would make the robot pick up a tray from the stall above it and serve the table below it.

Early finishers: Draw a hawker centre map on squared paper and write the shortest program to deliver two orders. Swap with a partner and test each other’s programs.

Answer key

One three-star solution per level, in Python. Other solutions with the same number of blocks earn three stars too. Jump links take the class straight to a level.

Level 1: Table for One

4 blocks

dotcodecampus.com/maze/hawker/1

move_right()
move_right()
move_right()
serve()

Level 2: Round the Corner

7 blocks

dotcodecampus.com/maze/hawker/2

move_right()
move_right()
move_down()
move_down()
move_right()
move_right()
serve()

Level 3: Pick Up First

8 blocks

dotcodecampus.com/maze/hawker/3

move_up()
pick_up()
move_down()
move_right()
move_right()
move_right()
move_down()
serve()

Level 4: Mind the Trolley

8 blocks

dotcodecampus.com/maze/hawker/4

move_down()
move_right()
move_right()
move_right()
move_right()
move_right()
move_up()
serve()

Level 5: Two Orders

11 blocks

dotcodecampus.com/maze/hawker/5

move_up()
pick_up()
move_left()
move_left()
serve()
move_right()
move_right()
pick_up()
move_right()
move_right()
serve()

Level 6: Lunch Rush

21 blocks

dotcodecampus.com/maze/hawker/6

move_up()
move_up()
pick_up()
move_down()
move_right()
move_right()
move_down()
move_right()
serve()
move_up()
move_left()
move_up()
move_left()
move_left()
pick_up()
move_down()
move_left()
move_left()
move_down()
move_left()
serve()

Bonus: Supper Crowd

23 blocks

dotcodecampus.com/maze/hawker/bonus

move_up()
pick_up()
move_down()
move_down()
serve()
move_up()
move_up()
pick_up()
move_left()
move_left()
move_up()
move_left()
serve()
move_down()
move_right()
move_right()
move_right()
pick_up()
move_right()
move_right()
move_up()
move_right()
serve()