CounterSide is a free to play tactical RPG for PC and mobile. Has a positively reviewed, F2P-friendly solo campaign. PC: https://store.steampowered.com/app/1976440/CounterSide/ Android: https://play.google.com/store/apps/details?id=com.studiobside.CounterSide iOS: https://apps.apple.com/us/app/counterside/id1309394370
