Growing and shrinking together

Challenge 3 of 16

Two sizes, two steps, and one of the steps is negative. The left circle swells while the right one drains away, from lines that differ only in a minus sign.

Set the left growth to 4 and the right to -4.

Your code JavaScript

Set the left growth to 4 and the right to -4.

Console print() output

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Lesson Growing and Fading

Position was never special.

x = x + speed looked like it was about movement, but there is nothing about movement in it. It takes a number, adds another, and puts the answer back. Plug the result into a shape's third argument and you have a size; plug it into shapeColour and you have a colour that changes. The line does not know or care.

A colour is three numbers.

shapeColour(red, green, blue), each from 0 to 255, exactly as in "Colour by Numbers". Give one of them a variable and it can climb or drain a step at a time. Equal amounts of all three make a grey, which is why fading one number in all three places fades a shape to black. Keep them between 0 and 255 — above that a colour stops being a colour and the shape simply stops changing.

Seeing a number with nowhere to show.

A position you can watch. A colour number you cannot really read off the screen. print() writes a value into the console strip under your code — scroll down past the editor to find it — one line each time it runs, so you can see what your own number is actually doing. It shows your sketch's output, not the target's — it is for understanding your own work, not for finding the answer.