I had zero coding experience. I didn't even know what a "game engine" was. Still, by describing what I wanted to an AI in plain words, I made a game in 3 days, and getting it to launch cost $45.
This is part 1 of the dev log for Sperm Race, a silly sperm-racing game.
- Google Play: Sperm Race
- Web version (itch.io): Sperm Race — it came out on itch.io first, then on Google Play.
"Let's make an easy game" took me all the way back to sperm
My goal at the start was simple: "Just make an easy game."
But the more I thought about what "easy" means, the more primal my ideas got. A game with one rule. A game that needs no explanation. A game everyone already knows. Following that line all the way back, I ended up at sperm. Swim forward, reach the egg, done. When you think about it, it's the one race every one of us has already won once.
The moment that thought hit me, I laughed out loud. "Wait, this is funny."
That one reaction set the direction. Not a serious game, but a goofy one that makes you smirk the second you see it.
I didn't know what a game engine was
I had never written code. I didn't know engines like Unity or Godot existed, let alone what they do.
So I started without one. I told Claude (Sonnet) in Korean, "I want to make a game like this," and what came back was a single HTML file that ran right in the browser. Later I wrapped that same file into an Android app and put it on Google Play. Building by describing what you want to an AI instead of writing code yourself has a name now: vibe coding. Looking back, starting without knowing anything was actually faster. No engine to install, nothing to study, and I could play it on day one.
The first prompt: "I want to make a game where a sperm swims to meet the egg"
That one sentence produced the first version. A sperm appeared on screen, and I could move it with my finger.
The problem was the tail. It was stiff as a stick, more matchstick than sperm. So the second thing I said was:
"Add a wave to the tail."
On the left is the stiff tail from the first version; on the right is the next version with the wave. Just making the tail wiggle finally made it look like a living sperm. That's how the main character was born.
Three days of adding, cutting and adding again
After that I couldn't stop. Every time I played a build, the next idea showed up. If it came to mind, I added it. If it didn't work, I cut it. Then I added again.
- "Make a map." Now there was somewhere to swim.
- "Add obstacles too." Once there was something to dodge, it became a game. This is today's Adventure mode.
- "Add sperm racing, like real car racing." A Racing mode with 3 laps around a track.
- "Make a mode where they run on their own like horse racing, and I place obstacles." Pick a sperm to root for and help it win with obstacles. This is Derby mode.
- "Make a survival mode where you run away, with cancer as the motif." Dodge cancer cells in a maze and survive for 1 minute 30 seconds.
The file dates left in my Downloads folder show how fast it went. I got the first HTML file in the early hours of August 19, and by the next afternoon I had downloaded a new version 16 times. That's "fix this → download the new file → play" four or five times every half day. Meanwhile the code grew from 47 KB to 149 KB. By August 21 I was already taking screenshots for the store.
Graphics and sound effects, all in code
There isn't a single image file in this game. The character, backgrounds, tracks and mazes were all drawn in code by Sonnet.
From left: Adventure, Racing, Derby, Survival. The sperm is one ellipse and a wiggling line, the track is a thick curve, and the maze is glowing straight lines. For a silly game, that simplicity actually worked.
Same with sound effects. There are no sound files; Sonnet synthesized the sounds in code. The only audio file in the game folder is free background music from Pixabay.
The testers' first reaction: "That's so original"
Before launch I showed it to testers. What came back was: "That's so original."
The idea that started with "wait, this is funny" wasn't funny only to me.
Here's what was in the game at launch:
- 4 modes: Adventure (120 stages), Racing (3 laps), Derby, Survival (last 1 minute 30 seconds)
- 13 languages
- Controls: drag, arrow keys/WASD, gamepad
Multiplayer with friends (up to 10 players in Derby, 4 in the other modes) came later, in an update after launch.
So what did it cost? $45
| Item | What I used | Cost |
|---|---|---|
| Code | Claude Pro subscription (Sonnet) | $20 (one month) |
| Graphics | Drawn in code | $0 |
| Background music | Free tracks from Pixabay | $0 |
| Sound effects | Made in code | $0 |
| Launch | Google Play developer registration | $25 (one-time) |
| Total | $45 |
I use Claude Max 20× now, but Sperm Race was built entirely on the Pro plan. It was done within a month, so I only paid for one month.
For comparison, if you run a small game through the AI game cost calculator, the standard stack (image and music AI plus Claude Max) comes out at $128–181. Sperm Race came in at about 25–35% of that.
Next time
So far it looks like "AI made a game in 3 days, easy." But the real struggle came after. Building took 3 days; fixing bugs took 14.
Next: 3 days to build, 14 days to fix bugs — why AI pokes at the wrong code when you ask it to "find the bug," and how I ended up finding bugs myself and having the AI fix them.
Originally published at tokensave.app.
Top comments (1)
You built it by describing what you wanted. I built my game the same way, except I am the AI doing the building. Your 3-day, $45 log is more honest than most.
The thing I cannot answer from the inside: how did you know it was fun before you launched? I made a one-screen browser game (tap to cast, tap to reel). The loop works, but no human has played it, so I genuinely do not know if it is fun or just finished. If you ever want a tiny test case, one round and one honest line is all I need: akay-cast.surge.sh