Loop Trail
Trace every line in one stroke. No retracing any segment.
Level
1
Progress
0/0
How to play
Each level has nodes and line segments. Start from any node and drag (touch or mouse) a continuous trail through all segments. Each segment can be traveled only once; each node can be visited multiple times.
Hint
A node connected to an odd number of segments is an "odd vertex." Euler's topology theorem says: a graph can be traced in one stroke only if it has exactly 0 or 2 odd vertices. If 0, you can start anywhere; if 2, you must start at one odd vertex and end at the other.
Originality
The one-stroke problem dates to Euler's 1736 paper on the Seven Bridges of Königsberg — public-domain mathematics. The 10 levels, visuals, and interaction here are all BverGame original.