Here are a few slides that outline the process I went thru to create the Mobile Game "The Big Apple". The point is to show you that you need to have a PLAN to begin with and then tackle parts in separate coding chunks. As I ran into challenges, like the Keeping Score (see below) I had to adjust my plans.
Tips For Success
Write down your thoughts - keep things in distinct stages and functions
Code and test in small chunks - test small functions, then move on
SAVE COPIES of your project as you go, so you can "Roll Back" to what works!!!! (super important)
Don't create a Frankenstein then try to debug everything at once
Do some research, CS First Videos, YouTube
Test the look and function on a Mobile Device - often!