Everything in the menu are platforms and I recommend jumping to the letter on the right.
Jump onto Credits, avoid landing center on the C. Aim for K unless you know what you're doing. Either way, this will play the Credits which will move over the screen and block your view. But with enough practice you can ignore this.

After landing on credits, aim for the volume icon. Then land on the edge of the icon underneath it because it's center is hollow. Or the plus sign which theoretically shouldn't do anything since it might be maxed by default.

Finally, land on the Quit sign. Try not to overshot and you will likely land on it, saving the game and closing it.

This way you can save your progress. Resetting the game(whether through Steam or other external shutdown and restart) will return you to your saved position.

Have fun collecting waifurs.