Your city makes one shape. Trains carry it from your factory out through your border gates to a rival.

Rivals send theirs to you. Build a depot for each shape that arrives and connect it to a line. Shapes headed further on get passed through another gate, and you earn a toll.

Lines: drag between your stations. Drag from a line's end to extend it, or back to its start to make a loop.

Overflow: a station holding too many shapes grows a red ring. If it fills, your city falls. Add trains, depots, or lines, or slow your factory down. It never stops.

Tricks: Bank output and release it as a Surge your trains haul out (the platform gets 7 seconds of grace). A Recycler remakes a rival's shapes as yours and sends them back. A Warehouse widens a platform. A Customs post triples tolls and slows rivals at a gate. Annex a fallen neighbour for its land, its gates and a second factory.

Hollow shapes are just passing through your city; solid ones are yours to deal with.

Win: be the last city running. After 6 minutes rush hour speeds every factory up.