NIGHT MAIL — Sorting Tower Seven

A mile under the city, the night train comes in and drops the sacks on the floor. Everything above that is your problem.

Sorting Tower Seven is a cast-iron shaft that runs from the sorting floor at the bottom to the pneumatic launch galleries at the top. Every parcel that comes off the train has to be carried, weighed, stamped, franked, read, and fired up the right glass tube to the right district before the shift clock runs out.

You never touch a parcel. You build the machine that does, you start the shift, and then you watch to find out where you were wrong.

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The loop

DESIGN → RUN → DIAGNOSE → REDESIGN.

1. Design. The shift is paused. Lay machinery on the tower's 9 × 24 grid from the Municipal Supply Ledger — belts, inclines, chutes, bucket lifts, splitters, mergers, address readers, stampers, frankers and launchers, each with its plate number and its price.
2. Run. Press START THE SHIFT. The train arrives, the sacks open, and the mail starts moving. From here you can only pan and zoom — the machine is on its own.
3. Diagnose. When something backs up, the jam alarm names the tile (JAM 6, 19) and the heat overlay reddens the line all the way down to whatever is choking it. A pile-up strangles itself slowly and in full view.
4. Redesign. Take the floor again, rebuild, run it again. Delivered mail pays; the purse buys better parts.

What you're playing for

A night is passed when you deliver the quota before the clock runs out. It is failed when the clock beats you, or when the floor chokes. Either way you get a Shift Return — Form NM/9, itemised: delivered, misrouted, expired, spoiled, lost, launched, peak backlog — and you go again.

Six nights, each introducing one thing that breaks the layout that worked yesterday: ordinary post, then fragile goods that will not take a drop, oversize that will not fit a gauge frame, cold-chain on a timer, live animals that must not be stamped, and finally classified pouches that need a sealed route of their own. Three of the six nights carry a rush that triples the volume at half past.

Controls

1 – 0	pick a part off the rack
[ ]	walk the ledger
Left mouse	lay the part
Drag	run a line of belts
Right mouse	lift a part back off
R	turn the part
Z / Y	undo / redo
C / V	copy a region / stamp it down
Q	pick up whatever is under the cursor
Esc	drop what is in hand

Click any parcel while the shift is running to see where it came from, where it is going, and every machine it has passed through.

The six districts

Albertine · Cannongate · Dockside · Holloway · Marsh End · The Heights — each with its own enamel colour, its own nameplate on the gallery, and its own glass tube out of the top of the tower.

Worth looking at

• The launch galleries at the top, where the tubes light up as a capsule goes.
• The heat overlay during a bad night — the whole jammed column glowing red through five floors of ironwork.
• The Municipal Supply Ledger, an illustrated parts catalogue with plate numbers and prices, written the way a 1930s post office would write one.
• BOROUGH IRONWORKS · SORTING TOWER VII · MCMXXXI, cast into the back wall of the shaft.

The screen is portrait. The tower is nine cells wide and twenty-four tall because that is the shape of the screen.

The mail must fly.