This week, I looked at the coins gain and pay systems for the app 'Forest'
Forest
An app about focus, when planting trees you can't use your phone, otherwise, the tree will die
The longer you plant the tree, the more coins you get
coins are used to unlock more types of trees
Coin Earning Rules:
When planting time is less than or equal to 20 minutes
t = time
1. [1]: Adding 1 coin ( similar to a bonus point for each session)
2. [ t/5]: Represents users can get 1/5 coin per minute
Conclusion: For users planting less or equal to 20 minutes, the coin is calculated at 1/5 per minute, and then add 1 coin as a bonus coin.
When planting time is more or equal to 25 minutes
t = time
1. [4]: '4' is a number that can control the overall coins that the user gets with the accumulation of time. After testing this number, I found the pattern below:
If change the number 4 at the beginning: if change 4 to 3, users can get extra 2 coins when they plant for double time periods; change to 5, they don't get extra coins; change to 6, they get less 1 coin. As a result, it chose to use 4 for the reason they want users to feel they are awarded in longer time period tree planting and at the same time don't want too many. So they picked the 4 to be added to the equation.
2. [t/5]: This is the portion that means the fixed coins users get per minute( 1/5 coin per minute)
3. [5*(t-30)/30]: This portion serves the function of a limitation, when the user plants for less than 30 minutes and greater than 25 minutes, instead of having positive coin rewards added to the rest of the equation, they will get minus coins. As the base reward coin for planting over 25 minutes is 4 coins, this portion will behave like a balance point. For trees that are planted over 30 minutes, this represents a 1/6 coin reward per minute.
Conclusion: For users plant trees longer than 25 minutes. the functioning of the equation can be divided into 2 situations(below 30 or above 30). When below 30 minutes, the 3rd portion of the equation will act as a minus function, otherwise the 3rd portion will represent 1/6 coin per extra minute.
Coin Spending Rules:
< 20 minutes: can only plant bush
>25 minutes: can plant bush or tree
Bushes: prices at 300/600/1200
screenshots in the APP
Trees: prices at 300/600/1200/2000
screenshots in the APP
calculation on how many minutes the user needs to gain 300 coins
On average, users can afford a new type of tree or bush after spending 820 minutes( around 13.6 hours. So this app sets the spending time to a minimum of 13.6 hours in order to start the basic functions.
Conclusion on the Forest APP's coin system:
For this app, from the equations, we can find out that the designers want the user to spend more than 30 minutes per time. 30 minutes acts like a dividing line that from this point, all the minutes that the user spends will entirely be added to the coin. Also, more time spent once will bring 1 more coin than splitting the time into small sections. For example, the users who spent 240 minutes at one time will get 3 coins more than the user who spent 60 minutes four times.
Overall, after calculating and analysing the equations of this mobile app, I've learned about the coin system in designing a functioning app or a game. Firstly, set up a basic number for the coins that users can earn per minute. Secondly, divide the system into different sections based on how long I want the users to spend on my app( at least 2 sections in order to satisfy different kinds of users, long-term users, and short-term users). At Last, decide how many bonus coins I want the users to have once they spent longer in the app(maybe also depending on the prices on the shop page).
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