It’s right in their sentence. They’re saying they want to end up with a game.

If someone came to you asking “how can I write a word processor so I can write a letter?” what would you advise them?

“I want to build a new game engine to learn how to do it.” “Right this way; here’s how I’d approach starting that long journey.”

“I want to build a new game engine so I can write a game.” “You should probably skip the engine step and go straight to making the game.”