The 2022 Mat and Its Missions

The mission 4 min

A new mat, a new season, and the same first question: what does this mat pay for?

Block 1 ended with a scored round on the 2021 house mat. Today you move into the garden, and you start where every competition team starts — not with bricks, but with the scoring sheet. By the end of the hour you will have a route across the 2022 mat, written down, argued over, and walked by hand.

The garden, station by station 5 min

Open the 2022 mat in the mat picker below and find all six stations before you read on. They are not arranged in a tidy ring the way the 2021 house was:

• HOME — the robot base pad, left of centre and low. Everything starts and finishes here.
• A — the swimming pool, top left, a long way up from HOME.
• B — the big tree, almost directly above HOME and much closer than A.
• C — flower bed 1, centre of the mat.
• D — the red patch, right of centre, roughly level with C.
• E — flower bed 2, far bottom right — the most remote station on the mat.

Two things are worth noticing straight away, and both will decide your route. C and E are the same kind of place — two flower beds — so whatever your attachment does at one, it must do at the other, and they sit at opposite ends of the mat. And E is far away from everything. A route that visits E in the middle crosses the mat twice.

Scoring actions, not places 12 min

Here is the habit that separates teams who finish from teams who run out of time. A mission set is not a list of places to drive to. It is a list of scoring actions, and driving is the unpaid work in between.

Write the set out as a table with one row per action. For each row you need three things:

• What the robot must physically do — reach it, touch it, move it, carry it, leave it somewhere.
• What it is worth. Straight off the scoring sheet.
• What it depends on. Some actions are only possible after another one has happened, and those chains fix parts of your route whether you like it or not.

Now divide each score by a rough guess at the seconds it will cost, and rank the rows. That ranking is your route plan in disguise. The cheapest points come first, and the expensive ones are the first thing you drop when the clock beats you — which it will, in lesson 16.

Build it — on paper 10 min

Two artefacts come out of this lesson, and lesson 10 cannot start without them.

One — the route card. Draw the mat from memory, then check it against the real thing and correct it in a different colour. Mark your station order as a numbered line: HOME first, HOME last, every station you intend to score in between. Write your reason for the order beside it in one sentence.

Two — the attachment sentence. One sentence, no more, describing what the attachment has to do physically. Not “collect things” — that is not a sentence an engineer can build from. Something closer to: it has to reach forward past the wheels, close on an object about the size of a fist, hold it while the robot turns, and let go on command.

The program — in words first 12 min

No blocks today. Write the run as pseudocode: one line per action, in the order the robot will do them, in plain language. This is the same habit you practised in lesson 1, and it matters more now because Block 2 adds an attachment — which means some of your lines are about the arm, not the wheels.

Keep each line to one action. A good line looks like:

• follow the line from HOME towards B
• stop square at B
• close the attachment on the object
• reverse for a moment to pull clear
• turn towards C

A line that says “go and get the thing from the tree and bring it back” is four actions pretending to be one, and it will hide the exact place your program later goes wrong.

Mark every line where the robot has to know where it is — squaring on a line, a colour check, a wall touch. Those marks are the moments your route survives or falls apart, and lessons 11 and 12 exist to make them reliable.

Tune it — cut the route down 9 min

Take your ranking and your route card, and answer three questions as a team. Write the answers down; lesson 15 will ask for them.

• If the run had to fit in half the time, what goes first? Name the mission you would drop and say what it costs you in points.
• Does dropping it break anything else? If another action depended on it, you have just lost two missions, not one.
• Where does E sit in your order? Argue this one properly. E is the far corner; visiting it early and visiting it last give very different runs, and there is no single right answer — only an answer you can defend.

Run it — the walk-through 6 min

Put your Block 1 base on the mat at HOME. Nobody programs it. One student pushes it by hand along the planned route while another reads the pseudocode aloud, one line at a time, and a third times the whole thing with a phone.

Stop the moment the reader says a line the pusher cannot carry out. That is a real bug, found for free, a fortnight before it would have cost you a scored run. Fix the line and start again.

Write your walk-through time down. It is optimistic — a hand is faster and cleverer than a wheel — but a route that cannot be walked inside the limit will certainly not be driven inside it.

The journal 4 min

WRO judges score the engineering journal alongside the run, and Block 2 gets its own entry. Today’s entry must contain:

• your from-memory mat sketch, with the corrections in colour
• the scoring-action table, with your points-per-second ranking
• the route card, and the one sentence saying why that order
• the attachment sentence — copied out on its own line, because lesson 10 starts from it
• the walk-through time, and the line that stopped the pusher