Download | 2023 Global Mobile App Advertising & Monetization White Paper


TOPSHOW | Advertising eCPM, ARPU doubled! Strategies for increasing advertising revenue of "Lost Castle"


"Lost Castle" is a Roguelike action game developed by Hunter Studio, an indie  game studio in China. It was released on Steam in 2016 and became the best-selling domestic game all the way to the top. More than 91% of downloaded users gave them positive reviews.

With its excellent game quality and user reputation, "Lost Castle" has won many global awards such as The official display of the 2016 Global Developers Conference, The best indie game of the China Indie Game Competition, and the Asian GameStart Players' Choice Award. In 2019, "Lost Castle" was represented by Leting Games and officially transferred to the mobile game platform. In the same year, it won The AppStore Editor's Choice of the Year and was shortlisted for four major awards in The TapTap Game Awards. According to official information, as of June 30, 2020, the cumulative registered users of "Lost Castle" exceeded 10 million.



Unlike the paid buyout system on Steam, the mobile game "Lost Castle" adopts a commercial model of "trial play + in-app purchase + advertising". Different levels of payment unlocking stages and game permissions are set according to the progress of the game. As a hard-core Roguelike action game, considering the user experience, it is not suitable to use interstitial, banner and native ad formats that easily affect player operations. Therefore, the game operation team chose to use rewarded videos that do not affect the user experience for advertising monetization.


In-game purchase

In-app purchase contents——

Hunter license (unlock story of the level), purchase soul crystal (in-game currency, which can be used to purchase personalized dress, such as skin, emoji, etc.), and expanded contents (new story maps).


Guide payment strategies——

Stage-01: free download and trial play (open 1 week +15 talent, allowing participation in online mode + chaos mode);

Stage-02:6rmb (open 2-3 weeks +50 talent, unlock the full story content);

Stage-03:18rmb (open all remaining weekly items + 110 talents, unlock daily challenges, leaderboards, team room creation functions);

In-app purchase discount: unlocking all licenses at one time only costs 18rmb, saving 6rmb.


In-game purchases


In-game advertising

Currently, there are 4 ad slots in game:

  1. Daily soul crystal reward (3 times a day);
  2. Watch the ad resurrection (2 times a day);
  3. Get random passive items at the start (5 times a day);
  4. Obtain additional transformation soul crystal (revenue settlement).


In-game advertising


Product operation key points

In order to seek better ways to increase product’s advertising revenue and user payment conversion, the "Lost Castle" operation team had an in-depth discussion with TopOn. After understanding the game experience and the advertising operation strategies used by the TopOn operation team, they found that game advertising revenue is mainly limited by the following two aspects:

  1. There are fewer in-game advertising entrances, the advertising scenes are less obvious, which leads to lower advertising display per user;
  2. The advertising platform is relatively single, which is greatly affected by the fluctuation of the single-platform advertising budget, and does not use the waterfall layering function to carry out refined operation of advertising.



Advertising monetization optimization strategies

Based on the demand for revenue enhancement and operational key points, the distribution team finally selected the advertising monetization plan of "increasing user stickiness + moderately increasing advertising revenue":


  1. Reasonably plan the game advertising entrances

Based on the characteristics of the game, the team only considers monetization methods for rewarded video ads. Let players actively trigger the display of advertisements based on the progress of the game, aiming to increase the advertising revenue while improving user experience, increasing user stickiness, and even feeding back in-game purchases. For example, watching rewarded videos can get a certain amount of "soul crystals" (in-game currency that can be used to purchase personalized items), and there is an upper limit control for viewing advertisements every day. If players want to continue to obtain "soul crystals", then they need in-game purchases . Another example is to watch the rewarded video resurrection (2 chances a day). Players need to restart the game to "dead" in the game. Use the resurrection opportunity to continue the previous game progress for free and attract players to continue to play the game.


  1. Aggregate multiple mainstream advertising platforms through TopOn

"Lost Castle" only accessed one advertising platform before accessing the TopOn mediation platform. When faced with a reduction in the advertising budget of a single advertising platform, the revenue impact is greater and it is easy to fall into a more passive situation. After accessing many mainstream advertising platforms through TopOn, when one of the advertising platforms is affected by budget, the priority can be adjusted in time according to the eCPM performance of each advertising platform in TopOn. The advertising platform with a better performance will be set in higher priority. The priority is increased to avoid sharp fluctuations in revenue, thereby improving the anti-risk ability of advertising revenue.



In addition, through the addition of multiple advertising platforms, "Lost Castle" can request low-priority advertising sources in turn when high-priority advertising sources do not return. Try to get advertising fills every time an advertisement is loaded, further protecting players Of each ad exposure opportunity.


  1. Real-time data + comparison of two sets of display data

TopOn's hourly reports can support users to view data status in real time. For example, to check whether the display is normal, whether the switch of the advertiser is successful, the number of impressions of the new advertiser after the switch, and the time period during which players are more active. Provide data support for further operational optimization.



The two sets of data are compared through the display provided by TopOn and the three-party advertising platform. If the two sets of data are significantly different, then investigate the reasons one by one. The comparison of the two sets of display data can effectively troubleshoot the causes of data abnormalities and reduce the risk of traffic waste.



Tuning effect

With stable user retention, the Android version's eCPM and advertising average revenue per user (ARPU) both increased by 200%-300%; the iOS version's eCPM and advertising average revenue per user (ARPU) both increased by 50%-100%.

Commercialization of indie games

When it comes to indie games, many people’s first reaction is hardcore games and paid buyouts. They rarely associate them with advertising monetization. The Lost Castle shows the industry another way to commercialize indie games: through Free download trial + advertising rewarded, in the case of stabilizing and improving user retention, stimulate users to pay for in-app purchases. Compared with the previous paid buyout method, this has improved the conversion of paying users, and to a certain extent, it also reserves space for subsequent new paid items of the product. For example, the September 3rd version of "Lost Castle" adds the third layer of DLC. The secret path of the ice cellar and the abandoned ruins on the fourth floor are unlocked by players for a fee.


Pay DLC added

The business model of the mobile game "Lost Castle" is of great reference to traditional indie games that advertised "hardcore" and "niche". The double high scores of AppStore 4.8 and TapTap 8.7 also prove that users have a strong understanding of the model of "Lost Castle". Compared with the commercial model of purely paid downloads, this model ensures that non-paying users bring stable advertising revenue without affecting the retention of core game users. At the same time, it further converts non-paying users, enhances users’ willingness to purchase in-app purchases, and realizes users expansion of scale and increase of income.