I don't see any major problems with it. The main thing that might be a little clumsy is this:
The game's idle speed is adjustable. Most players can finish within several minutes, and there is also a speedrun leaderboard.
This doesn't really flow as a paragraph, and I don't think it needs to be in the blurb at the top, either. It might be better as a list of features, like this:
- Adjustable idle speed
- Fast-paced rounds - only a few minutes
- Leaderboard for speedrunners
Just a thought. The only other thing that bothers me a little is using the word "army" twice in the second sentence. Maybe change it to "Recruit and upgrade your troops"?