This is as simple a neural network I can think of. 2 inputs and xOR decision and on output. An xOr decision means:
off output if neither input is on or both inputs are on. On output if either of the inputs are on but the other one has to be off
0, 0 = 0
1, 0 = 1
0, 1 = 1
1, 1 = 0
Click LearnXOR() then select which sets of inputs you want to test. this is fairly complex but many Neural Networks will have a similar structure
Tensorflowjs xOr Neural Network.
Click the button to train the network. Pull down the select box to test
Training