I'll try that exercise myself asap, but my estimate would be more on the order of 3 hours or so.
Of course I'll have to look up a lot of things (I'd do it in HTML 5, so I'd have to double check the API for either Canvas or DOM). I suppose if you know the API mostly by heart it would help a lot.
In fact your article inspired me to put more effort into knowing the APIs. Could be because I was a Java developer for the most time that I got into the habit of always looking stuff up, even if I already knew it - I just felt like double checking a lot. Or maybe knowing the API could be substituted by a good IDE that suggests everything?
What are the rules for speeding up the ball in Arcanoid? :-)
It speeds up when it hits the paddle. If you do this exercise, make sure to actually time yourself, rather than guesstimate it afterwards - time slips away when you program.