This document discusses the use of random events and probability in game mechanics for free-to-play mobile games. It addresses common issues like game designers not understanding probability theory and outlines different probability distributions that can be used like uniform, Bernoulli, and normal distributions. The document provides advice on using random events like making sure player expectations match outcomes, random events should be significant but not dominant, and analyzing how random events affect all game systems.

1. Creative Mobile Games
Aleksey Rehlov
Secrets of Random Events Used in Game
Mechanics of Free-to-Play Games

2. Chance, Luck and Other Stuff
2

3. Outcomes
3
 Getting head
 Getting tail
 Getting ridge
 Hover in the air…

4. Monty Hall problem
4

5. Main uses in games
5
 Random rewards
 Random in game mechanics
 Generated content: levels, encounters, tasks and etc.
 Creating of the unique experience
 Increasing of replayability

6. Main issues with probability in games
6
#1
The most part of gamers know
nothing about ProbabilityTheory
and Mathematical Statistic

7. Main issues with probability in games
7
#2
The most part of game designers
know nothing about Probability
Theory and Mathematical Statistic

8. Main issues with probability in games
8
#3
And the most part of those, who
are familiar with them, don’t
understand how to use it in games

9. Reward and its probability
9

10. Brute force solution
10

11. “Bag” solution
11

12. “Sequence” solution
12

13. Random events in game mechanics
13

14. Issue of a small amount of experiments
14
Mathematical
probability
Statistical
probabilityWTF?

15. How to make: 𝑃 𝐴 ≈ 𝑃∗
(𝐴)
15
 Dynamical correction of probability with
provision for all previous results of events
 Automatic or manual generating of a
result sequence

16. Probability distribution
16

17. Uniform distribution (discrete)
17

18. Bernoulli distribution
18

19. Normal distribution
19

20. Some advice
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1. Outcomes of game events and players’ expectations from them have to tend to
the same result.
2. Effect of random events on the gameplay has to be significant, but not dominant.
3. If it is possible to avoid random in a game, then avoid it.
4. Make sure you analyze how one or another random event affects all game
systems and processes.
5. Do not reinvent the wheel.
6. If you are not familiar with probability theory and mathematical statistic, then try
to find a specialist before creating any random in a game.
7. The rules are made to be broken 

21. 21

23. Aleksey Rehlov
a.rehlov@gmail.com
aleksey.rehlov@creative-mobile.com
Creative Mobile Games, 2015
Any questions?
White Nights, Moscow, 2015