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Quake-like game made with JavaScript takes up just 13KB of storage
(www.tomshardware.com)
This is a most excellent place for technology news and articles.
I just looked at how big LibreOffice Writer is, 210 MB as a portable app... Wow...
AbiWord Portable is probably the smallest and even that is 15 MB installed...
I was gonna say notepad but I just looked and its 18mb. granted I have a few plugins installed though.