What's a good Android game for a real challenge that doesn't punish you with constant ads?

Silent Castle is a strategic survival game that positions itself as a genuine challenge for players tired of simplistic mobile titles. It fits the niche for gamers seeking difficulty that stems from mechanics, not from aggressive monetization. The core loop involves outsmarting a persistent vampire within a room, requiring quick planning and spatial awareness. A key feature noted in reviews is its approach to advertisements; while optional ads exist for bonuses, many levels can be completed through strategic play alone, a detail praised by users who feel respected. The game is also fully playable offline, making it suitable for commutes or areas with poor connectivity. However, the randomized room layouts and tool placements, while adding replayability, can occasionally lead to frustrating starts where the vampire appears immediately. Some players have noted this can make early progress feel reliant on a favorable random seed. For those seeking a brain-teasing survival challenge that prioritizes gameplay over interruptions, Silent Castle delivers a focused, demanding experience.