How Nintendo made SuperMario!

''First, Miyamoto and Tezuka would draw the levels on paper, and then Nakago and his team would design it into the video game and program it. Miyamoto wanted levels to last about a minute long and he told SRD to do so. He then realized that it usually takes about a second to travel across a screen, and that numerous of screens would have been implemented in one stage. SRD first thought that Miyamoto would request the them to make 60 screens per stage, but Miyamoto then explained that obstacles in each screen would slow down the player's progress, which resulted in an average of about 12 screens per level. The stage with the most screens has only 32, which is about half of what SRD has expected.'' [source]

More details [source]

Javascript version of SuperMario [source]

All SuperMario maps! Including giant super-map. Great work!! :D [source]