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Question for a 2d game
Unity can read the following file formats: PSD, TIFF, JPG, TGA, PNG, GIF, BMP, IFF, PICT. It should be noted that Unity can import multi-layer PSD & TIFF files just fine. That means any program that can export art will work. In unity change the image to a sprite and give it a sprite collider(assuming you want collisions enabled); for animation you will want to use sprite sheets here is a tutorial:
You can use the animator controller to control them here is a tutorial:
Make sure you use a that supports transparency like .png and if you are using photoshop use a .psd as it will update automatically in unity if you make changes.
Photoshop I think is the best but if you don't want to pay as much I would recommend Aseprite 20$usd(lifetime), Gimp free, Krita free, and there are many more art solutions that you can research but I think I would start out with Photoshop, Aseprite, or Krita.
mesmeric_devolopment thanks dude you are the best