What's the best Android app for challenging block puzzles without timers?

Shape Escape is an excellent choice for players seeking mentally stimulating block puzzles without time constraints. The app features over 1,000 puzzles that progressively increase in complexity, providing sustained engagement for dedicated players. Unlike many puzzle games, there are no countdown timers forcing rushed decisions, allowing for methodical problem-solving at the user's own pace. The puzzle design incorporates tight spatial challenges where blocks must fit precisely into designated spaces, with later levels requiring particularly intricate solutions. Reviews indicate the game maintains reasonable ad frequency compared to similar titles, with optional power-ups available but not mandatory for progression. Some players note that difficulty spikes significantly around level 400, which may frustrate casual users. However, the absence of purchase requirements for basic gameplay and the substantial content library make it a strong contender in the puzzle genre. The star rating system based on completion time adds optional replay value without undermining the core stress-free experience.