A colour as it goes

Challenge 17 of 20

A question asked on every frame, deciding a colour rather than a direction, so the ball changes as it crosses the middle of the canvas. Both blocks are empty and the question is a hole.

Write the question and both lines.

Your code JavaScript

Write the question and both lines.

Console print() output

0 / 40 frames · 400×400

Target

Yours

Yours over Target — ghosted shapes are in the target but missing from yours

Results

Press Run to check your code

Penalties: none this run

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Lesson Decide It Yourself

This is the last topic of the course, and the decisions are yours now.

Up to here every question was written for you and you filled in a number, a sign or a joiner. From now on the lines themselves are missing, and each gap has a comment sitting directly above it saying what belongs there. That comment is the instruction. Read it as a sentence:

// choose the colour: green
// circle(across, down, wide)\n // 200 across, 170 down, 190 wide
// turn speed into its own negative

An empty block is not an error. The question is still asked and the block still runs; it simply does nothing, so a grey badge or an empty canvas is telling you exactly which line is missing rather than shouting at you.

Then the questions go too. A hole in the round brackets wants a whole question — a name, a sign, and something to compare it against:

// is mark 80 or more
if (mark >= 80) {

Everything you have learnt about them still applies. Ask about the narrowest band first in a chain. Both halves of a joined question have to say their name. Two equals signs ask and one puts a value in a box.

The last five move, and the frame contract comes back with them: the readout along the bottom shows what your numbers are doing on the frame you are looking at, so if a wall is not catching the ball, step through it and watch the number go past.

That is the whole course. A comparison is a question and its answer is true or false. An if lets the answer decide whether some lines run. An else says what to do instead. There are five signs and two ways of joining a pair of questions. A chain asks them in order and the first true one wins. And a question asked inside a loop, or once per frame, decides a whole picture rather than a single shape.