I’m not sure why free will is considered such a mystery. In a completely deterministic universe my actions are determined unambiguously by a) the current state

I’m not sure why free will is considered such a mystery. In a completely deterministic universe my actions are determined unambiguously by a) the current state of my brain and b) the inputs I receive from my senses. Asking if I could do something other that what I actually chose to do makes no sense. On the other hand, if I later find myself in a near identical situation I may choose a different action as a result of my brain now having a different state (that’s what learning is) The opposite of determinism isn’t “free will” it’s random behaviour and who wants their decisions to be random?