Choose Interaction > Handles > Translate.
A handle is added to the hat so that after it is published on a web
page the surfer can drag it around. Notice the Interaction Editor
at the bottom of the screen; a sensor (MouseSensor2) is linked
to a reaction (Translate1Hat)
Turn on the Browse button to preview the scene as it will appear when
it is published. Click and drag the Hat to test the new interaction.
You will notice a few things:
To create the World, you worked in Author mode. By switching to Browse
mode, you can preview how the World will look and act on a
web page.
When you move the cursor over the hat, it changes to a hand, indicating
that it is interactive.
When you release the hat it snaps back to the snowman's head. This
was achieved using a Snap Constraint.