Bolts

Bolts are the in-game currency to buy upgrades in the Endless game mode. During every stage, you can get three bolts by these methods: finishing a mission, getting the bolt somewhere in the stage and/or reaching stations.

The bolts can be used for various upgrades to your train. You can either upgrade an already existing wagon to perform better. You can buy a new wagon that can fulfill another task or you can upgrade your engine. Upgrading your engine will slow down the train and will allow you to move into a new biome.

Special (orange) bolts are available only once per biome and count as two regular bolts. They are furthermore necessary to unlock the final engine.