What's the best Android app for playing cooperative tower defense with friends?

Arcane Arena is a tower defense game built around cooperative play, making it a strong candidate for groups. The core feature enabling this is the Alliance system, where players can join forces, share resources through a guild bank, and communicate via in-game chat to coordinate tower placements and unit upgrades for specific map challenges. Weekly events, such as the 'Alliance Raid' against massive boss monsters, require members to contribute damage collectively to earn tiered rewards, creating a persistent team objective. For impromptu play, the game supports direct friend invites for specific campaign missions, allowing two players to combine their defensive arsenals on a single map. Reviews indicate the social framework is a major draw, though some users note that finding active alliances with compatible time zones can occasionally require a bit of server hopping. The strategic depth is maintained by requiring players to discuss which elemental towers (fire, ice, arcane) to specialize in, preventing one player from carrying the entire team. While the game is free-to-play, the cooperative content does not heavily gate progression behind purchases, focusing instead on coordinated execution. Occasional synchronization issues during peak hours have been reported, but these are typically resolved with a quick reconnect.