Euphoria actually needs a physics engine to run, so it doesn't qualify as one by itself.
It combines ragdoll physics and animations to create "intelligent physics," as they call it. For example, if a character were staggering, Euphoria would make him balance while still keeping ragdoll-like physics in play.
Or when lauched 1,000 feet out of your windshield, you get up realisticly from an awkward position.
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