A tunnel isn't dug, it's assembled. This prototype puts you on the segment erector: win the liner-truck battle to stack six precast segments, then raise the ring in augmented reality — physically aim your phone at each red slot until it locks green and shake to install — before the machine snakes away. The same method that lines a bore on Earth becomes, on Mars, the shielded corridor between sealed domes: the smallest playable piece of the Flat Mars thesis. Prefer the calm desktop version? →