Instructions...

The condition we want to test is that we have an ordering of the vertices so that if a-b-c-d is in an induced subgraph, and they follow the following criteria a < b iff d < c (and also c < d iff b < a).

Create a graph to test on the left. Left-click to add vertices. Left-click a vertex to highlight it, and then left-click another vertex to add an edge. To remove an edge, left-click one of its vertices and then right- or middle-click the other vertex. Vertices can't be removed as of now (however you can refresh the page to start over.)

To see the constraint di-graph, click the button labeled "Generate constraint graph." To see the components of the constraint graph, click on appropriate button above. To brute-force test the graph on the left, click that button labeled "Brute Force Check" Brute-force is only fast enough for graphs up to about 8-10 vertices.
Note: Some of these features don't work for graphs with more than 100 vertices.

For either side, click and drag a vertex to move it.