Balancing with numbers

Too hard, or too boring?

Before you joined, Kai and Remy ran a test of Garden Defense. Wave 3 sent 40 beetles and nobody survived. In another test, the snails were so slow that players got bored and wandered off.

Both problems are just numbers. Tuning a game's numbers so it feels fun and fair is called balancing.

All the numbers in one place

Garden Defense keeps its numbers in one data file called balance.json, outside the code. A piece of it looks like this:

"beetle": { "speed": 40, "health": 3 }
"sunflower": { "cost": 50 }
"wave1": { "beetles": 5 }

To make beetles slower, we change one number and no code changes. Later, a tool called Remote Config (Stage 9) can even change these numbers on players' devices without a new app update.

The difficulty curve

• Easy startThe first waves teach you. A few slow pests, so you can learn how planting works.
• Rising challengeEach wave asks a little more: more pests, faster pests, new kinds of pests.
• BreathersAfter a hard wave, an easier one. A calm moment before a boss. Time to feel strong and catch your breath.

The difficulty curve is how the challenge changes over time. A good one looks like a roller coaster climbing a hill, not a wall.

Numbers that grow

Writing every wave by hand gets slow, so designers use a formula, a rule that works the number out.

• Adding (linear): beetles = 2 + 3 x wave. Waves 1 to 4 get 5, 8, 11 and 14. Steady growth.
• Multiplying (exponential): each shield upgrade costs 1.5 times the last. It starts slowly, then shoots up.

Multiplying suits prices, because players earn more as they go. Adding suits enemy counts, so waves never explode out of control.

Fair or frustrating?

Losing is part of games. What matters is how it feels.

Fair: you lose, you know why, and you think "next time I'll do better". A Hyper Shards boss with an attack pattern you can learn is fair.

Frustrating: you lose and don't know why, or it feels like the game cheated. A boss that fires bullets nobody could dodge is frustrating.

Change one number at a time

Say you make beetles faster, plants cheaper and wave 3 bigger, all at once. Now the game feels worse. Which change caused it? There is no way to tell.

So balance like a scientist: change one number, play the game, write down what happened. Then the next number.

Save each change as a commit, a save point in the project's history, with a clear note like beetle speed 40 to 35. If it was a bad idea, you can go back.

You're too good at your own game

Testing after every change is important. But there is a catch: the team has played these games hundreds of times. A wave that feels easy to us might be impossible for someone new.

To find out how the game really feels, we need fresh eyes.

Bolt says: Next lesson: playtesting, the best way to see a game the way a new player does.