What Is Some Good Mature, Harem, Ecchi Manga?

Some interesting websites






Puzzles, problems and challenges:

http://www.recreomath.qc.ca/
http://www.ac-amiens.fr/pedagogie/associations/adcs
http://membres.lycos.fr/croco/PROB / enigmes.html



puzzles and puzzles to build:

http://www.archimedes-lab.org/atelier.html