Our game Gravity Sling is a free app with 15 levels included and another 30 levels available via In App Purchase (IAP). It was one of the first titles to take advantage of Apple’s new policy of allowing IAP from within free apps.  Apple announced this policy change on Thursday October 15th, and we submitted in the wee hours of the morning on Monday October 19th. It was approved by Apple on Thursday November 5th.

We’ve always thought that free+IAP was a better way to go for most small-form and simple titles that typically sell for $1.99-$.99 on the app store. Ultimately it provides a better experience for the end user while allowing developers to provide an easier upgrade path for “Lite” users who want to go full. However the issue is not whether or not we think it’s a better way to do things, but if end-users agree and that this type of model can result in a sustainable business.

With that in mind, we have been tracking our sales and a few other metrics fairly closely since launch, and this post is the first of what will likely be several posts in the coming weeks and months sharing our results thus far.

Results so Far

Gravity Sling has found some limited success already. It has not (yet) been featured by Apple, but we did get a few decent reviews on iPhone game sites, and several blogs picked it up. In the US, it has been ranked between 25 and 50 in free Puzzle and free Strategy consistently since launch. The most success however has come in Italy and Japan, where Gravity Sling climbed up the Free app charts peaking at #10 of all free apps (#3 of all free games) in each country.

Gravity Sling ranking graph as pulled from MajicRank (highly recommended utility!)

Conversion Rate

The most important data point we want to know is the overall conversion rate. That is, what % of users who download the game decide to purchase a Level pack via IAP. Right now our overall conversion rate is 1.91% so approximately 1 out of every 50 people who download Gravity Sling purchase our level pack for $.99. This compares favorably with the typical conversion rate of .7-1% seen in many PC downloadable casual games.

In actual #’s we have had 66,346 downloads of the app from Nov 5-Nov 22nd and 1,267 sales of the first (and currently only) level pack.

Purchase Timing / Delay

We expected there to be something of a delay between a user downloading Gravity Sling for the first time, and when they decided to purchase the Level Pack. What we found is that this is somewhat true, and the delay seems to be about a day, however the delay also appears to increase over time. That is, for the first few days Gravity Sling was available, there was little to no visible delay between downloads per day and purchases per day. 2 weeks later, we’re seeing that purchases seem to happen 1-2 days after download.

Gravity Sling's global download totals and Level pack purchases per day

Regional Variation

We have found significant regional variation to our conversion rate. To date almost 85% of our downloads have come from Japan (25,705), Italy (18,434) and the US (13,709). 80% of our purchases have come from the same three countries with the Japan leading (486), followed by the US (406) and then Italy (143). This results in a conversion rate for the US of 2.96%, Japan is at 1.89% and Italy is all the way down at .78%. Or to put this another way, US users are 3.8 times more likely to purchase a level pack than users in Italy. The difference between the US and Japan is much less pronounced with the US having a conversion rate 1.5 times higher than Japan.

Gravity Sling downloads and purchases by day for the US

Gravity Sling downloads and purchases by day for Japan

Gravity Sling downloads and purchases by day in Italy

The OpenFeint effect

Perhaps the most interesting and somewhat unexpected result we’ve found is the correlation of OpenFeint usage on purchases. As of last night 55% (36,980) of all Gravity Sling players had submitted a score to one of the leaderboards (which happens automatically for anyone signed into OpenFeint). However 73% (925) of all users who had purchased a level pack were OpenFeint users and had submitted a score to one of the leaderboards. Digging into this further, what we found is that OpenFeint users are almost 3 times more likely to purchase a level pack than non-OpenFeint users. Our conversion rate is 3.4% among OpenFeint users and drops to 1.2% for non-OpenFeint users.

Conversion rate % for OpenFeint and non-OpenFeint users

Also interesting here is that it appears OpenFeint users are more likely to purchase early. In the first few days of app availability over 5% of OpenFeint players bought a level pack, and that has since dropped to our current 3% level.

Non Monetary Discoveries

While we still believe that Free + IAP makes the most sense for games like Gravity Sling, there are some tradeoffs aside from the pure technical implementation. Most notably was with regards to reviews and trying to generate media attention at the launch of Gravity Sling. While many sites did cover the game, there were several which would not stating that as a matter of policy, they did not review free applications.

We also were forced to limit Gravity Sling to iPhone OS 3.0 so any users (primarily iPod Touch users) who had not paid to upgrade to the latest OS were unable to play Gravity Sling.

Anecdotally we’ve also heard that some users were confused by the In App Purchase, and would have liked to have bought the game if they knew how.

The surprising thing here is that there was very little to no user backlash at having paid content in a “free” app. We expected this to be a huge concern since this was one of the first free apps with IAP content, but we have not seen any complaints about this yet.

Conclusions (for now)

Based on our sales data to date, we can make several conclusions:

• General conversion rate for IAP is around 2%
• Region matters as US conversion is 2.96% while Italy was just .78%
• OpenFeint usage is corollary to purchase as OpenFeint users convert 3 times higher than non-OpenFeint users.

Next Steps

We’re submitting v1.1 of Gravity Sling to the app store very shortly, and are hoping to learn a lot more once that is released. With v1.0 we did not do a good job of letting the user know that a Level pack was available to purchase. With v1.1 we’ve added a couple upsell screens to make this more obvious (though hopefully not super annoying!). We’ve also created 2 new level packs so we can start to learn how many people will purchase multiple level packs.

To address the issues of getting reviews, and allowing OS 2.2.1 we will also be releasing a “Premium” version of Gravity Sling for sale. This version will not have any In App Purchase, but will come with everything in the game already unlocked. While our focus will still be on pushing the free+IAP version of Gravity Sling we’re hoping that the premium version will pick up sales from OS 2.2.1 devices, and other users who aren’t able or willing to do IAP.