2D Shadows?

You will have to design shadow sprites in a program like PhotoShop or GIMP I believe, then program them to play animations or scale them.

design shadow in photoshop and import this to Unity

There are a number of assets on the store for this (shameless plug alert, we wrote one of them): https://www.assetstore.unity3d.com/en/#!/list/1354-lights-2d-resources

There are a couple of popular algorithms for casting 2D shadows. One is to create a visibility polygon and draw over your scene like in this article: http://ncase.me/sight-and-light/ There is a forum thread about that method here: https://forum.unity3d.com/threads/2d-dynamic-shadows.165283/ My favorite algorithm has always been the hard shadow algorithm from this article since it's so easy to implement: http://archive.gamedev.net/archive/reference/programming/features/2dsoftshadow/page3.html Super Fast Soft Shadows is basically that algorithm, but upgraded with shaders to render accurate penumbras.