Getting on Steam is a good way for an indie game to generate sales. However, you'll need to do a lot of promotion to get there. The current process for an indie to get onto Steam involves getting users to vote for your game. If enough people vote for your game you get on Steam. "Enough" is some value that moves around and isn't public. Valve has recently started letting more games on through greenlight so this may be getting easier to do than it has been in the past. If you search you should be able to find blogs by devs that used this route and copy some of their strategies.

The game looks good for something made by a 14 year old but it's unlikely to get any press from major gaming sites because it isn't unique enough. Now is an especially bad time to try to get their attention because GDC is next week. They'll already be flooded with stories to write.

Your son may have some success building word of mouth by posting it a few places like reddit. There are subreddits for indie gaming and for game development he could post a link from. If this doesn't work don't try again right away because it will come across as spammy and give the wrong kind of publicity. Asking for feedback on those boards should also get some useful advice.

Ah OK: Ah OK - I see where you can submit games there: http://steamcommunity.com/workshop/about/?appid=765&section=...

Also noticed Gog: http://www.gog.com/indie

And Desura: http://www.desura.com/development

Are all of these basically equal? The HN cloud seems partial to Steam...

How about Steam?