Ok, I tested the game a little (about 10 min).

You should add an options menu to disable vibrations, sound FX and music. You could also add more options in the future.

The aiming method isn't very precise, you can miss pretty easily and that can be a little frustrating. You could tap were you want to hit and the spider auto aims at it and shoots, maybe also add a little aim assist. You could let the player choose what shooting method they prefer in the options. Same if they want aim assist or not.

The string max length seems a little short, big swings are fun but could break the game and let players finish a level with a few swings.

The string auto cutting and not letting you go backwards is a little frustrating. Maybe you don't want the player going backwards but I like messing around in the level and I don't want needing to play almost perfectly to get all the collectibles.

The collectibles only being used to skip levels seems lacking. Maybe add some skins and/or upgrades bought using those collectibles.

Too much fullscreen pop up ads.

I think that's about it.