Objects appear, coming from the side of the screen and the player has to avoid them and jump over them. Alternatively or, another type of enemy could emerge from higher on the screen and the player would have to duck to avoid them.
The objective of the game would be to get to the end of the level, which would be achieved after a certain amount of time has passed and the player has survived the waves of enemies. The character will remain in one spot, most likely, or will only be able to move on the screen. This will not need a scrolling background. However this may look strange if the objective of the game is to reach somewhere.
The objective of the game could be changed to survive the waves of enemies and the time, to complete a stage. With the ability to still move freely around the screen, however this may be difficult to emulate on a touch screen device. However it could be achieved by setting the controls of the character to be that of the mouse, which would in turn allow the player to move the character by dragging and swiping their finger across the screen. Which would be a smoother control system than having onscreen buttons or, to force use of the number pad, because not ever device would have access to one, and use an on-screen one.
The waves of enemies would be related in some way to that of the main character. For example if the main character was a fox, the enemies could be hunting dogs, or something related in that sense.
Because the main character would not be moving, much, only two sprites would be needed for the character. The enemies would only need one sprite, because they will only pass through the screen. The main character will need a jumping sprite and an idle sprite.
