Publisher Chillingo has dabbled in freemium iOS games before, but it's generally prefered to stick to its favourite 99c price standard.

Perhaps the re-booting of Monster Mayhem, previously released for 99c in May 2010, but now also available free with in-app purchases, suggests a new direction.

New ways to pay

The game, a castle defence game that gained a Pocket Gamer Bronze award, has been reworked with in-game currency Coins, available from 99c, €0.79 or 69p for 10,000 or $5.99, €4.99 or £3.99 for a million coins. You use the coins to buy weapons include a flamethrower, machine gun and atomic bomb.

You can also now unlock all stages of the game for $2.99, €2.39 or £1.99.

Significantly, the full game remains available for iPhone at its standard price with IAP, while the freemium version is available here [iTunes links].