The answer is - via Playstation Mobile. Officially supported devices are listed here and include most modern Sony devices plus the HTC One V / S / X / XL / X+ and Evo 4G LTE. Packing one of those devices? Head on over to the Playstation Mobile download page to get started.
If you don't rock one of those beauties and you're feeling brave, this thread at XDA Developers discusses getting the app running on unapproved devices (i've had varying levels of luck with this).
When you have PSM up and running, click Games -> Puzzle Games and you can download for free.
So what's the PSM version like? It's OK. It's a pretty faithful port of the levels themselves, but with a 'Worms' style graphical and audio twist. Why Worms style you ask? Because the port has been created by Team 17, creators of the (awesome) Worms franchise. The worst thing about the conversion? The original music hasn't been carried over. Nooooooooo.......
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