Do you need more proof that free works?

Probably not, but to hammer another nail into the coffin of the business plan you gave the bank manager last year comes a case study from Australian developer The Voxel Agents.

It's released two iOS games, Train Conductor and Train Conductor 2 (oh and what you say Flipper? Dolphin Hero too, apparently).

On the rails

The former two provide solid track-based entertainment, but until this week hadn't really challenged the top of the App Store - although the series has historically sold more than 140,000 copies.

Train Conductor 2 made it to the nominations for the Independent Game Festival in China, which encouraged The Voxel Agents to set the original Train Conductor free via FreeAppADay.

In five days, it's been downloaded two million times, becoming #1 in 25 countries, and in that cross promotional way, this has boosted Train Conductor 2 up the paid charts.

At time of writing, it's #16 in the US paid charts, peaking at #9.