Let me introduce you my current project !!
it's a 3D map editor and it's made with CSS3 and Javascript !!!
for those who don't know, these languages are basically used to make websites.

eventually a game will be added to play inside the maps :) AND you'll be able to play in maps other players have created !! by the way you'll be able to post your's too !;)

for now it still in early developpement ( only 4 intensive days ) and all the basic editor functionnalities are done Yayy !:)