Stage 1 

Your nanobot is injected into a neuron at the start of each level and you move it by dragging it with your finger from that neuron to the next neuron along an axon. An axon is a long arm extending from the neuron and ending in a network of sub branches called a dendrite. A neuron may have as many as three different axons extending from it. Note that there is a limit to how fast the nanobot can move - no matter how quickly you drag it.

Start and end 

Axons are one-way paths, you cannot easily travel back up an axon, so try to avoid dead ends! Prior to version 2.0, if (when) you do need to backtrack, you must use the return button. For versions 2.0 and higher, you can simply back up by tapping the previous neuron (sliding won't work). Should you reach a dead end, you will be told to reverse course.