Hi, everyone! As most of you should be comfortable with x86 assembly by now, I thought I'd share the book/collection mentioned in $subject. xchg rax, rax [1] is a collection of riddles written in assembly, most of which rely heavily on the various behaviours documented in the x86 instruction set. [1]: http://www.xorpd.net/pages/xchg_rax/snip_00.html Lucian