Is there a good iOS app for a connecting puzzle game that feels challenging but not stressful?

Flow Free is a longstanding puzzle game centered on connecting matching dots with pipes to fill a grid. It fits the niche of challenging yet low-stress gameplay because the rules are instantly understandable, but solving larger grids requires increasing logical foresight. The app excels for this use case through its graduated difficulty, offering hundreds of puzzles across various grid sizes. The mechanic of drawing lines is tactile and simple, avoiding time pressures or penalties for mistakes, which reduces frustration. Reviews indicate users find it a 'very fun and challenging puzzle game' that’s excellent for mental engagement. A specific feature is the ‘Shapes’ pack, where connecting dots creates recognizable outlines, adding a visual reward to the completion. However, some user feedback points to the presence of ads, even after purchase, which can interrupt the relaxed flow. For sessions on a commute or during a break, the game provides substantial content without complex rules, making it a reliable choice for methodical puzzle fans.