Stephen Wolfram: Language, Mathematica, Alpha, Lab, Etc. 

[[https://www.stephenwolfram.com]]

Language, Introduction:

[[https://www.wolfram.com/language/elementary-introduction/2nd-ed/]]

Cloud:
[[https://www.open.wolframcloud.com/env/wpl/GetStarted.nb?funnel=WPLExplorations#sidebar=explorations

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Physics:
Visual Summary
[[https://www.wolframphysics.org/visual-summary/dark/]]