Balance the times of the levels because some levels are too permissive
when it comes to how much time you have in them in normal difficulty

Add hard mode

• Starts with 1 life
• Reduces each level's timer that is over 5 seconds by 2 seconds
• When you reset the level you lose 1 life

Update some levels to not include 1 block gaps
Change level 3 completely to have a better difficulty increase
Change the last levels where you run in straight line to include some blocks

some formatting of files

• Add new line at end of each file
• Remove trailing spaces where there are any

Add polish to the looks of

• Main Menu
• Game Over
• Game Win

make sure that when lives reaches to 0 game ends instead of -1

Add fade out effect between scenes