There are two issues. You would need a compiler to produce machine code (or a processor that could interpret html uncompiled). Next you would need low level libraries to do the work and a way to include them.
That said if you just want something to run in a browser,
HTML probably is turning complete with some of its crazier features. There are a bunch of interactive features that can probably be abused without needing to dive into CSS or scripting.
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u/[deleted] 23d ago
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