I played this game start to finish in one sitting, and yet I can't really rate it that highly. The real "content" in this game is unlocking new tools for destroying spiders and the controls are just a teensy bit too clunky to fully enjoy all of them (guns especially feel just a tad too inaccurate). There are a lot of challenges though, for those that want them - there are always enough easy ones that you can pass the level with relatively little effort, but the more involved ones can be quite difficult, especially as the game goes on.

20 USD for this (full price) feels a little bit steep, but the current Winter Sale price of $9 feels like a good deal for what you're getting, assuming you're not a completionist. You can also easily play this while watching youtube videos, as you don't really need any audio cues and there's nothing time-sensitive. This is the kind of thing I look for when I'm buying casual games.