Das Balancing eines Spiels ist eine große Herausforderung, insbesondere wenn es gilt, Spieler auf unterschiedlichen Niveaus gleichermaßen abzuholen und im Flow-Kanal zu halten. Dabei spielt die automatische Anpassung des Schwierigkeitsgrades eine zentrale Rolle. An dieser Stelle kommt das Konzept des AI-Directors ins Spiel, welcher erlaubt die Balance zentral zu steuern und dynamisch an das Spielerverhalten anzupassen. Wie dieses Konzept konkret umgesetzt wird und sich auf das eigene Spiel übertragen lässt, erklärt Sascha in diesem Talk.

1. @swagentrotz
Blazing Badger

2. @swagentrotz
Blazing Badger
Who is talking?
Sascha Wagentrotz
CEO, Co-Founder and Game Designer
Blazing Badger GmbH
Founded in April 2014
Based in Frankfurt, Germany

3. @swagentrotz
Blazing Badger
Softography

4. Keep your game in the fun zone
Designing an AI Director

5. @swagentrotz
Blazing Badger
Why would your game not be fun?
The challenge structure is unstable.
The challenge parts don’t combine the way they are supposed to.

6. @swagentrotz
Blazing Badger
Specific Problems
Spawn camping
Getting one-shot
Button-mashing to victory
Out of ammo/Stuck on low health
Farmed up to invincibility
Difficulty affects enemy damage/health only

7. @swagentrotz
Blazing Badger
Why does this happen?
Challenge flow is static
Spawn timings are pre-determinedin most cases
Enemy distribution is pre-defined
Each enemy is allowed to make its own decisions
Enemies don’t take the actions of other enemies into account

8. @swagentrotz
Blazing Badger
Solution: AI / Combat Director
DOES:
Controls all elements of the challenge with perfect knowledge
Enforces specificdynamic
Adjusts on the fly within seconds
Offers many parameters to affect difficulty
DOES NOT:
Make the game easier if you play badly!(if done right)

9. @swagentrotz
Blazing Badger
WTF is an AI Director?
Superordinate Entity that takes control of the “big picture” of your game and features a dynamicsystem for game dramatics, pacing and difficulty.
Has been around for decades in simple forms
Was adapted for more genres over the last years

10. @swagentrotz
Blazing Badger
Process: MDA Framework
Mechanics DynamicsAesthetics
The experience (Aesthetics) that arises, when the player interacts (Dynamics) with the game rules (Mechanics).
Therefore:
What Dynamicsdo we want to see?
What Mechanicsdo we employ to facilitate them?

11. @swagentrotz
Blazing Badger
DYNAMICS
What we want:
Smooth challenge flow
Mixof initiative and reaction
Some degree of forgiveness
Achieved with:
Spawn Rate
Attack Behavior
Recovery Rate

12. @swagentrotz
Blazing Badger
STRUCTURE
Intention
Definition of the goal
Dynamic
What happens
Mechanic
How to get there
Parameters
Our “balancing knobs”

13. @swagentrotz
Blazing Badger
Spawn Rate -Intentions
Good players are unable to ever beat the spawn counter (spawn camping)
May even need to put heavy pressure onto enemy numbers to survive incoming damage on higher modes at all
Bad players can never be swamped more than as intended by a tightly designed worst case

14. @swagentrotz
Blazing Badger
Spawn Rate -Dynamic
Spawn rate depends on number of enemies present, desired maximum numberand time to max number
The lessenemies present, the fasterthey spawn
Enemy Amount
Time
Enemy amount over time
Most fights will happen here

15. @swagentrotz
Blazing Badger
Spawn Rate -Mechanic
The n-thenemy spawns after F(n) secondsafter encounter start
F(n)=((n/MaxAmount)^Exp)*MaxTime
The n-thenemy spawns once a certain amount time has elapsed since spawning the previous one:
SpawnTimer=F(n)-F(n-1)
Restart the counter every time an enemy spawns
Time
Enemy #
Time elapsed when nth enemy spawns
t until next enemy

16. @swagentrotz
Blazing Badger
Spawn Rate -Parameters
MaxAmount, MaxTimeand Exponent
Depend on enemy strength and encounter intensity
Manage multiple pools for different challenge categories
Larger desired max number of small enemies
Lower desired max number of strong ones
Lower time to max for “deal with it” like spawn behaviour
Larger time to max for “you cannot ignore this for long” behaviour

17. @swagentrotz
Blazing Badger
Attack Behavior-Intentions
Groups of two should not be boring
Groups of six+should be tough but beatable
The playershould have the initiative most of the time(ratio ~ 2:1 to 3:1) The player should be frequently forced to react
Very high intensity situationslike bosses may changethe initiative/reaction ratio(~1:1 or even 1:2)
The amount of players present shouldn’t influence the challengemuchfor an individual player

18. @swagentrotz
Blazing Badger
Attack Behavior-Dynamic
The enemy attack frequency depends somewhat, but not much, on actual enemy numbers
The player has enough time to dispose of 2-3 foes before reacting to something
The time between attacks dependsa lot on enemy typeand the attack’s strength
On lower difficulties, there is lessneed toreact in time than on higher ones
If multiple players are present, each player is pressuredmore or less evenly (enemy proximity and attacks)

19. @swagentrotz
Blazing Badger
Attack Behavior-Mechanic
All challenging enemy actions have a cost associated
Enemies who are in positionto act registerall their currently possible with the Director very frequently (simultaneously)
The CD selects an action to be executed from what was registered, and incurs its cost in “debt”
The debt degeneratesback to zero over time
Actions can onlybe ordered at zero debt
Makes sure attack cost has no unwanted impact on how often has a chance to be bought
Manage likeliness by other means (e.g. chances, or multiple debt counters)

20. @swagentrotz
Blazing Badger
Attack Behavior-Parameters
Per actor:
Action Cost
Combat Director
One to several debt pools
Initial debt for each pool
Degeneration rate for each pool (does not have to be constant)
Degeneration
Enemy #
Enemy amount over time

21. @swagentrotz
Blazing Badger
Recovery Rate -Intentions
The player shouldn’t be able to hoard beneficial items (as this would trivialize bigger challenges that come along later)
The player shouldn’t ever be so starved for items that he cannot afford to use one every battle or two
There should be no extreme spikes in the drop rate

22. @swagentrotz
Blazing Badger
Recovery Rate -Dynamic
The drop rate of beneficial items should depend on the amount of items already in the player’s possession
The more items the player has, the less likely it is another one will drop
It should not happen that items keep dropping even though there are already plenty waiting to be picked up

23. @swagentrotz
Blazing Badger
Recovery Rate -Mechanic
Items waiting to be picked up count as well
Chance(Possesion)=base^(Posession)
0 < base < 1
Possession=Carried+x*OnGround
X = factor for value of items on the ground e.g. 0.5 = 50% worth
Drop Chance
# in Possession
Time elapsed per enemy

24. @swagentrotz
Blazing Badger
Recovery Rate -Parameters
Base
OnGroundModifier (x)
Example:
Possesion= Carried+x*OnGround= 0+0.5*0 = 0
Chance(Possesion)=0.5^(0) = 1 = 100% drop chance
Possesion= Carried+x*OnGround= 1+0.5*1= 1.5
Chance(Possesion)=0.5^(1.5) = 0.353 ~ 35% drop chance
Chance(Possesion)=0.7^(1.5) = 0.585 ~ 59% drop chance

25. @swagentrotz
Blazing Badger
Variants
Want player to wait for opening
Have enemies buy whole sequence
Or regular low/freeze combat point generation
Want moments of frenzy
Occassionally lower costs by large factor
Want hard limits on some attacks/spawns
Add cooldown
Other Genres: e.g. Hint-Directorin a Puzzle Game

26. @swagentrotz
Blazing Badger
THX
follow me on twitter! @swagentrotz
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enjoy gamedev;)