No problem! The sling shot controls are popular on many mobile games becuase of how versatile it is. You can get a lot of mileage out of it by adding layers and gimmicks on top of it.
another good inspiration is the Peggle series by popcap games. that gave you power ups and extra score depending on what you hit. one of the power ups lets you see the trajectory. I did also get reminded of another game where you play as a ball that must adsorb other balls of the same color to expand and get bigger. I can imagine a mode where you have to combine like colored objects and be mindful of their size, and as you progress, the core gets bigger. I could name other games like the zuma and luxor game series where you have to time things to combo multible same colored objects, or bloon tower defence where you can set turrets, or heck, classic asteroids and break out! but you get the jist. I can see potential with this by giving different control options and experiment with gimmicks and gameplay layers. I say play video games you like and take notes!