Making a Choice with if

💡 The idea

An if lets the program compare two numbers and act only when the answer is yes.

• if side > 60 [ colour red ] means: if side is bigger than 60, switch to red.
• You can compare with > for bigger, < for smaller, and = for exactly equal.
• The work that depends on the answer goes inside the square brackets.
• When the answer is no, the program skips the brackets and carries on.
• Put the if inside a loop and the answer can change from round to round.

📘 Words to know

if

do something only when a test is true

condition

the question an if asks

compare

check whether one number is bigger, smaller or equal

👀 Watch this

Six squares growing out of one corner. The ones bigger than 60 come out red.

set side 20
repeat 6 [
if side > 60 [ colour red ]
repeat 4 [ forward side right 90 ]
change side by 20
]

▶ Run it below

✍️ Your turn

1. Run it and count how many squares turned red.
2. Change 60 to 100 and predict what happens before you run it.
3. Change > to < and run it again.
4. Add a second if for a second colour: if side > 100 [ colour purple ].
5. Try if side = 60 [ width 10 ] and see one square get a fat outline.

🎯 Challenge: Use both < and > so that small triangles come out blue and big ones come out orange.

set r 20
repeat 6 [
if r < 60 [ colour blue ]
if r > 60 [ colour orange ]
repeat 3 [ forward r right 120 ]
change r by 25
]