You can create a click animation by composing two "scale" animations. You can find this under the "custom" tab when adding an animation onto a layer.
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The first animation should be a scaled down, and the next one should scale the cursor back to a 100%.
Repeat the process on the button being clicked and voilà. For an even more immersive experience, you can also add a little click sound!
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You can find a complete video tutorial on our Youtube Channel:
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You can also check out this file for a complete example: https://jitter.video/file/?id=FtV3cslZ6Ko7vL1aCaRPe