You've made an endless runner type of game yet you've tried to go against it. I mean, is it just me or "good" endless runners are fast and/or quite stressful. The whole Relax theme is kind of a bad choice.
About the music and sound effects: It's an endless runner, don't throw at me remix of Minecraft's open field theme. Also boosting sounds more like hitting a brake button in an old racing game than accelerating.
About the visuals: The trees in the background look nice but what am I actually? Some 3D block and sphere glued together? C'mon. You can do better than that.
If this is really your first game though it's pretty nice and I'm waiting to see some progress.