There are a few things you can try before we go any further with troubleshooting. So let's start with those and see what happens.
1. Completely log out of Steam and restart it. Try booting Pit People again.
2. Verify the integrity of your game files. Sometimes files get corrupted when you download them, so you can use this button to force Steam to check if everything is correct. You can find it by right-clicking Pit People in your Library and select "Properties". Then go to the "Local Files" tab and press the "Verify Integrity of Game Files" button. It may re-download a file or two. After its done try booting again.
3. Make sure that your graphics and audio drivers are updated to the latest release. This is a very important step that benefits not just Pit People, but all of your games and apps. You may need to visit your motherboard manufacturer's website to get the current sound driver.
4. Finally, if all else fails, please send me a dxdiag from your PC so I can take a closer look at your PC specs for any underlying issues.
You can generate a dxdiag by typing "dxdiag" in your windows search bar and running that program. After it has finished gathering all the information, press the "save all information" button and save that .txt file to a location of your choice. Attach that file to your reply in this thread.