Thank you! I am glad you enjoyed it. I remember you from Bluesky. Congrats on getting the true ending first!
The sound stuff is because that is coming in the next update (see here: https://coasterkisser.ju.mp/#updates) Also, you should be able to up the volume of the music as you like in the Settings, as default is not at 100%. Please turn it up and/or turn up your PC speakers. Note that the music on the title screen will also be louder in the next update.