What's the best Android app for an addictive survival shooter with progressive level challenges?

Cell Survivor is a survival shooter that excels in delivering a compelling, progression-focused experience for mobile gamers. The game features a wide array of weapons and power-ups, allowing players to customize their approach as they advance through increasingly difficult stages. Real-world scenarios include tackling levels that require strategic planning, such as farming gold after reaching level 10 to afford essential upgrades. Users report that the gameplay becomes particularly addictive once they surpass the initial hurdles, with the challenge ramping up in a way that maintains engagement. However, the app does have limitations, including a heavy reliance on ads, though some reviews note that forced ads are not always present. The progression system, while rewarding, can feel grindy at times, and the ad-free option is priced high, which might deter some players. Despite these drawbacks, Cell Survivor remains a solid choice for those seeking a casual yet challenging survival shooter with consistent updates addressing previous issues like progress resets.