Going free-to-play can be a huge gamble. Giving away a vast portion of your game for nothing, after months or even years of development, is a risky business.The successes are widely documented. Games like Temple Run and CSR Racing make big headlines and big revenues, dominating the top grossing charts.Yet, as with any business model, there are plenty of failures too. And, while some of the mistakes might seem obvious in hindsight, the results are no less devastating.The creators of Gasketball, Punch Quest and Monkey Drum learned this the hard way.All three games failed to convert high download numbers into in-app purchases. The results were disastrous.Here the developers highlight their mistakes and share some of the lessons they learned in creating a relatively new phenomenon: a popular failure."The most important change when doing IAP instead of a paid app is that your storefront is now your responsibility," says Mikengreg's Mike Boxleiter.Alongside Greg Wohlwend, Boxleiter spent two years developing Gasketball, a shot-matching basketball title with a level creation spin.Gasketball inspired positive reviews and over 200,000 downloads, but in-app purchase conversion rates of just 0.7 percent.Gasketball picked up downloads aplenty, but stuggled with IAPs"iOS users are trained to look for the data in the areas Apple has set up; big juicy screenshots and lines of bullshit review scores on how awesome everyone thinks the game is," says Boxleiter."If you go freemium you throw that out the window and now you have to make the sale yourself. Now it's like Glengarry Glen Ross, remember your ABCs."Gasketball, Punch Quest and Monkey Drum all failed to do this by poorly signposting their IAP options.In the case of Gasketball, Boxleiter says, "We got a lot of early feedback saying the IAP options were hidden or confusing.""So we quickly threw together an update which plastered the metaphorical walls of the game with upsell ads, big 'Unlock the Game' buttons everywhere."The lesson is clear: Fail to alert players to IAP and they will be unable to invest in it.Flippfly's simple music game and song creator Monkey Drum suffered similar problems, driving just 20 percent of users to its in-game store.But this wasn't Monkey Drum's only mistake. According to Flippfly's Aaron San Filipo the game also failed to correctly identify its audience."We hoped that a very young audience would have fun with the 'play the drums and watch the character repeat your rhythm' feature and that an older audience would get hooked on the song creator," says San Filipo.Monkey Drum dev Flippfly misjudged the game's audienceMonkey Drum's IAP model was built around the assumption that both groups would want to unlock new instruments by bypassing the game's progression system and spending real money.But Flippfly made a fatal misjudgment."Once we shipped the first version, we realised from the feedback we were getting that it really appealed more to a very young audience, as opposed to the variety we'd hoped for," says San Filipo."Most of our audience was content to just bang on the drums and watch the characters repeat their rhythm."As a result very few players were incentivised, or even capable, of investing. Monkey Drum achieved a conversion rate of just 0.5 percent."If we were to do it again, we'd make the song creator the main feature, and tune it towards an older audience who'd be more likely to pay," says San Filipo.Proper incentivisation is a concept RocketCat misjudged when creating the endless runner variant, Punch Quest.Punch Quest features an in-game currency used to unlock new powers and abilities, with coin packs available via IAP.But despite 200,000 downloads in its first few weeks on sale, Punch Quest bought in little more than $10,000.Punch Quest was critically acclaimed"While most free games make you wait minutes or hours between upgrades, we pretty much give you an upgrade or new ability or power every single match," says RocketCat's Kepa Auwae."We have tons of them, but it turns out that the total length of the progression matters way less than the time between upgrades."The trick, says Auwae, is to space the upgrades out."The iOS audience seems to love grindy games, for the most part," he says. "I think it has to do with how a lot of mobile games are played, just a few minutes at a time."A grind in a mobile game gives a sense of permanence, or of building something up."And of course, it also provides players with an incentive to buy IAP shortcuts, something Punch Quest - with its frequent showering of free rewards - did not.To encourage IAP conversion you also have to make it clear to players just what they will gain from parting with their cash.That's a lesson that Mikengreg learned by building Gasketball's IAP around driving players to multiplayer, where they felt the game was strongest."Initially we had the single-player game segmented into four pieces which were each 99c, and when you bought a level pack you got two new items to use in multiplayer, which increase the fun of making levels dramatically," says Boxleiter."We wanted to use the IAP model to entice free players to play against paid players who had awesome stuff, which would inspire the upsell.""In the end very few players even tried the multiplayer out, so the major factor we used to decide how we sold the game ended up being irrelevant."As a result, players were not able to experience the game at its best, a flaw that Boxleiter believes was fatal."You have to make the value proposition very clear," he says.Following their release Gasketball, Monkey Drum and Punch Quest were all subject to a set of quick-fire updates, in an attempt to rectify their shortcomings,Storefronts and IAP options were tinkered with, values were increased and extra consumable items were introduced.Yet the updates all failed to make a substantial impact on conversion rates, leading Punch Quest and Monkey Drum to abandon free-to-play entirely.Gasketball, meanwhile, took a slightly different approach, introducing an "unlock everything" IAP option."I looked at it as a free demo which would seamlessly unlock the full version of the game," says Boxleiter. This approach also failed to make much of an impact.What Mikengreg, Flippfly and RocketCat discovered was that if a games design fails to properly embrace free-to-play monetisation, no amount of skin deep updates can rectify the situation.You have to get it right upon release.One way of attempting this is extensive testing and analysis during development, identifying and optimising how players interact with your game.Flippfly's San Filipo believes it is essential, yet for Mikengreg's Greg Wohlwend there is no such thing as an easy solution."We talk with a lot of developers," says Wohlwend. "And everyone has a different story, something that really worked for them and they're convinced it'll work for you."In one instance I know a developer who spends months - months! - researching IAP conversion, running A/B tests and every other trick in the book to maximise everything they can."It's all valid. That approach can really work."But I know that same developer just released a game and it did peanuts after months of research and development."It's a really polished game, but: peanuts, even compared to Gasketball probably.""The art and business of making video games is too complex to distill into some kind of bulleted list of failsafes and gotchas," says Wohlwend."Even the company with perhaps the most resources of any developer in the world, Zynga, made enormous mistakes with Draw Something."Yet despite this the market leaders do provide some valuable lessons, as exemplified by free-to-play poster child CSR Racing.An example to all? NaturalMotion's CSR RacingNaturalMotion's car management and racing title continues to succeed because of what it offers players, not what it holds from them.While Gasketball and Monkey Drum put up a paywall in front of content, CSR Racing's IAP rewards players with something they love: cars. It doesnt feel like a tax to continue playing.Meanwhile, Punch Quest failed at free-to-play because it rewarded players far too readily and easily, thus negating desire.So perhaps there are no easy answers to avoiding a popular failure. But by learning from Mikengreg, Flippfly and RocketCat's mistakes, you can at least give yourself a fighting chance.