Game Play ideas

I need to think more of how the game play would be. After researching games such as Robot Unicorn Attack, Drain Works, Cut the Rope, Angry Birds and others I realized that the most simple games were the most popular. To make my game simple but addictive would be my main goal.

At first, my game was to be a 2D action/adventure game but then I looked to making it more simple; 2) here shows the game play if you were playing it portrait and shooting upwards whereas 3) has a more 'helicopter' style of gameplay which appealed to me more.
This has more promise as it requires only one button: hold to go up, release to go down. I want to add another button to the game: shooting enemies (tapping, possibly) and maybe even collectible power ups and/or super attacks that can be used to wipe out several if not all enemies on screen.