mode: add-nodes
Click anywhere on the canvas to place a node.
0
Vertices (V)
−
0
Edges (E)
+
0
Faces (F)
=
?
V − E + F
Euler's Formula
For any connected planar graph: V − E + F = 2
Isomorphism tip
Two graphs are isomorphic if one can be redrawn to look like the other. Use Move mode to drag nodes and reshape your graph — the structure stays the same!
Faces & regions
A face is a region bounded by edges — including the outer (infinite) region. In Colour faces mode, click the outer face button in the top-left corner of the canvas to colour it.
How to use
1. Add nodes → 2. Connect them with edges → 3. Move nodes to explore isomorphisms → 4. Colour faces to verify V − E + F = 2.