help on control newly developed stim

[Guest guest]

my 27 mo son recently becomes obsessive of looking at things from the

side of his eyes. He would run back and forth in from of a fence for a

long time to get the visual effect. He is so obsessed with it that he

would throw a tantrum everything we distract or interrupt him. We are

worried that this new stim will narrow his interest span further as he

seems less interested in playing with us or having other activities

recently. Can anyone who had similar experiences give us some

suggestions on how to deal and control? Many thanks.