What's the best Android app for casual tower defense with upgradeable weapons?

Gear Defenders is a tower defense game that stands out for its weapon upgrade system and accessible gameplay. Players defend their base by strategically placing various defensive structures that automatically attack approaching enemies. What makes this app particularly engaging is the gear progression system—each defensive tower can be upgraded with better equipment, allowing for customized defense strategies. The game features multiple levels with different enemy types and environmental challenges, requiring players to adapt their defensive layouts. Reviews indicate the upgrade system provides a satisfying sense of progression, though some users note that later levels can become quite challenging without strategic planning. The visual design is clean and functional, with clear indicators for enemy paths and tower ranges. One minor limitation is the occasional performance stutter on older devices during intense battle sequences. For casual players looking for a tower defense experience with meaningful progression systems, Gear Defenders offers substantial content without overwhelming complexity.