Princess Rescue: Save Girl

This is a game where you often see things like buses and thread winding, categorized by color. Even when you try to strategize the order, it often doesn't work out, so watching ads is necessary. You can get items/coins, expand the base, and revive through ads. However, you can ignore ads other than for revival (revival is a game-changer because it allows you to clear all used bases and expand the base at once). The caution here is that if you proceed with upgrades using purple items, you'll only increase the time you survive without being able to do anything, pushing you further away from achieving your point-earning goals. Once you've expanded, you can't undo it later. For the ads that play after each clear, on my Android version, I could skip them by returning to the home screen. It seems enjoyable enough for killing time.

It's a simple game, perfect for killing time.