Introduction to Computer Science with MakeCode for Minecraft

Lesson 6: Conditionals

Computer programs are made up of instructions that tell the computer how to process input

and deliver output. In Minecraft, the instructions you write are triggered by events or by

commands, and they control what actions take place in the Minecraft world. An important part

of programming is telling the computer WHEN to perform a certain task. For this, we use

something called ‘conditionals’, because a certain Condition or Rule has to be met before an

● “If your homework is done, you can play video games.”

● “If you do your chores all week, you get your allowance, else you are grounded.”

These are all conditionals! Conditionals follow the format of IF this, THEN that.

IF (condition is met), THEN (action performed)

Have the students share a few conditionals from their own lives with the class or within small

groups.

NOTE: For older students, you can have them add the ELSE portion of a conditional.

Example: For the ‘IF it is snowing, THEN wear boots, ELSE wear shoes’ conditional, notice that

without the ELSE action, your students might end up not wearing any footwear!

Unplugged activity: Simon Says If Then Else

A quick variation on Simon Says to practice conditionals (If, Then, Else statements).

How to play:

hand, Else sit down.” So, everyone who has brown hair should have their right hands raised, and

everyone else should be sitting down.

Teacher tips:

• Lead the activity to practice conditionals with simple instructions, yet visually different

physical poses

• Check that students have correctly executed the instructions based on the criteria

• Read out the Conditional statements slowly and clearly

• Make sure students understand and are following along with each set of statements

• Reset the students to normal standing positions between each conditional statement

• If you play soccer, Then kick your feet (be careful not to kick anyone)

• If your favorite ice cream flavor is Chocolate, Then stick out your tongue, Else make

rabbit ears behind your head

• If you play a musical instrument, Then snap your fingers, Else whistle

• If your favorite monster in Minecraft is a Zombie, Then make zombie noises and

movements, Else jump up and down

Other example conditions:

• Your hair is brown / blond / red

• Your eyes are brown / blue / green

• You are wearing a sweater / shorts / T-shirt / pants / skirt / sneakers / sandals

• You have a sister / brother / no siblings

Types of Conditions in MakeCode

MakeCode for Minecraft features a special

conditional block called an IF… THEN… block.

There is also another related block called IF…

If you click the little plus sign at the bottom of these

blocks, you can add more conditions.

By default, there is a pointed-end spot for a block that says “true”. If you don’t change this, then

anything that the “If… Then block” encloses will run every time, because “true” is always true.

However, you can substitute another block, or a combination of blocks, next to the If, as long as

they ultimately are true or false, and fit in that pointed-end spot.

that area. But you can specify ~0 -1 ~0 to check the block the player is currently walking on, or

even use a Position range to detect the presence of a certain block within a given area.

In this chapter, we’ll explore some of the possibilities that the different conditional blocks

provide, by automating some common Minecraft tasks like chopping down trees or mining.

Then we’ll challenge you to create your own independent project automating some other

Minecraft task of your choice. Let’s go!

Activity: How Old Are You?

In this programming activity, students will practice using the Conditional If Then Else block in

MakeCode. They will code a program that uses a condition to compare their friends’ age with

their own, and print different messages if they are younger, older or the same age.

4. From the Logic Toolbox drawer, drag an If then else block under the On chat command

block

5. Click the Plus (+) sign in the If then else block to create another “Else if” clause

6. From the Logic Toolbox drawer, drag a Less than (<) Comparison block into the If slot

replacing ‘true’

7. From the Logic Toolbox drawer, drag an Equals (=) Comparison block into the Else If slot

9. In the second slot of the Comparison blocks, type your age (for example 12)

10. From the Blocks Toolbox drawer, drag 3 of the Print blocks onto your Workspace (or you can

right-click on one block and select Duplicate to make a copy)

11. Place one in each of your If, Else If, and Else clauses

12. In each of your Print blocks, type a different message for people who are Younger than you,

your Same age, or Older than you. Keep this message short – just 1 or 2 words.

13. Use the drop-down menu in the Print blocks to select a different block to use for each

message

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It is hard to predict which direction the Agent will be facing when you summon it. That’s why

directional commands are handy. But can you do without them?

You can omit the “tp” and “lt” commands and put everything in the “chop” program by doing

the following:

• Have Agent teleport to player be the first command when you call “chop” while standing

at the base of a tree.

• While the Agent is NOT facing a block, have it keep turning left. See if you can get the

Agent to stop once it is facing the tree trunk, then continue the program as normal.

have to trim some of the low-hanging leaves away. But you may be able to think of a way to

In addition to chopping trees for wood, you will probably also want to mine the earth for

precious minerals. One good strategy for finding the rarest of minerals, diamond, is to tunnel

deep beneath the earth to levels Y12 or Y13, then create a series of branching tunnels off a

your Minecraft world. Make sure you equip yourself with a pickaxe and torches to make some

room and see down there!

In this activity, we’ll create a basic mining Agent that automatically destroys blocks in front of it

and collects everything. We’ll use conditional statements to test for precious minerals. The

Agent is one block tall, so we’ll send it forward 64 blocks, then have it turn around, move up one

block, and come back. If the Agent finds anything of value, it will let us know and collect the ore.

4. From the Player Toolbox drawer, drag an On chat command block to the coding Workspace

5. Rename this On chat command to “lt”

6. From the Agent Toolbox drawer, drag an Agent turn block and drop it under the On chat

command “lt”

We can only mine diamonds in Survival mode, so the first thing we should do is make sure we

change the game mode to survival.

8. From the Gameplay Toolbox drawer, drag a Change game mode block and drop it in the On

Chat Command “mine” block

9. In the Change game mode block, click the player selector drop-down menu to select

“yourself @s”

to run. In our case, we want to give an alert if the Agent finds valuable blocks like gold or

diamond ore.

11. From the Logic Toolbox drawer, drag an Equals (=) comparison block out and drop into the

If then else block replacing “true”

12. From the Agent Toolbox drawer, drag the Agent inspect block into the first slot of the Equals

(=) comparison block replacing the number 0. The Agent inspect block will check the block

13. From the Blocks Toolbox drawer, drag a Block block out and drop into the second slot of the

Equals (=) comparison block replacing the number 0

14. In the Block block, use the drop-down menu to select “Diamond Ore” as the block we are

checking (you can also use the Search bar to find it)

If we do find Diamond Ore, then we want to print a message to the screen, and mine the ore.

Otherwise, if the Agent doesn’t find Diamond Ore, he should simply destroy the non-valuable

block in front of it, and move forward without collecting anything.

18. From the Agent Toolbox drawer, drag the Agent destroy block and the Agent move block

and drop them into the Else clause of the If then else block

Now we want to repeat this process 64 times, so we’ll use a loop.

19. From the Loops Toolbox drawer, drag a Repeat loop out and drop it after the Change game

This will send our Agent forward to mine 64 blocks. But we need to have her turn around and

come back. So, we’ll use another loop outside our Repeat loop – this is called a “Nested Loop”

since it’s a loop within a loop.

21. From the Loops Toolbox drawer, drag another Repeat loop out and drop it after the Change

game mode block, and surround our existing Repeat 64 loop

22. In the Repeat loop, type in the number 2, since we’ll just want our Agent to mine two rows

of blocks

At the end of the first row, we want our Agent to move up and turn around.

23. From the Agent Toolbox drawer, drag the following 4 blocks out and drop them in order

under the inner Repeat loop: Agent destroy, Agent move, and 2 Agent turn blocks

24. In the Agent destroy block, use the drop-down menu to select “up” as the direction

25. In the Agent move block, use the drop-down menu to select “up” as the direction

for Minecraft supports boolean operations, which are more complex conditions that are true if

one or the other condition is true (“or”), or if both of the conditions are true (“and”).

AND operator: both conditions must be True

OR operator: only one of the conditions must be True

26. Open the Logic Toolbox drawer and drag a Boolean Or block into the If then else block

28. Drag both of these Equals comparison blocks into the first and second slots of the Boolean

Or block

29. In the second Equals comparison block, use the drop-down menu on the Block block to

select ‘Gold ore’ as the mineral to check for

In this case, the If statement will run its code if the block is in front of the Agent is diamond ore,

OR if the block in front of the Agent is gold ore. If either of these is the case, we say “We’re rich!”

then destroy the block forward (which will drop the diamonds or gold ore) move forward, and

collect them. Otherwise, the Agent will simply destroy the non-valuable block in front of it, and

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