Imangi Studios Harbor Master HD has seen a number of additions since its original iPad launch in April. The base game includes a single map and can be downloaded for free, but theyve since added four new maps for $0.99 each as in-app purchases. The map above is called the Bermuda Triangle and includes pirates, monsters and cyclones to make your line-drawing life a bit more difficult.

But with the latest updates, theyve also added a clever rewind feature that lets you restart the game right before that last fatal mistake:

Weve also added a really cool feature rewinds. With rewinds, after you crash, you can choose to rewind or undo the crash, and continue playing where you left off. You can only use ONE rewind in a game, and you get a limited number of rewinds total. When we launched the update, we gave people 5 rewinds, and then they could earn 1 rewind for each 1000 pieces of cargo they ship. So they more you play, the more rewinds you earn, and therefore you can use a rewind more often.

You start off with 5 rewinds and can use one in any particular game. Rewinds are then earned for longer play time or can be purchased via in-app purchase $0.99 for $2.99 for 20, $4.99 for 40.

Balancing in-app purchases is always a challenging problem for a developer. On the one hand, in app purchases need to offer a legitimate value in a consumable product. But that product cant be one that gamers feel is a necessary component of the game. I feel like the rewinds fill this sort of niche well, and Id expect well see it more often in the future. As an added bonus, Ive always thought the compelling feature of these chaos management games is the "oh no" last second regret when death comes suddenly. Now you get a second chance.