itch.io

You're on the right track so I'll leave the design to you but I could see many different things going into this. Maybe hidden traps? Chance to drop an item on enemy death. Treasure chests.  Maybe a super meter/revenge bar. Different forms of mission (escape to a certain panel, save another robot, fuel a giant robot/vehicle), etc. Maybe an "upgrade disc" loot drop or something that allows your player to get small upgrades like max energy or +1 weapon damage to a specific weapon. Weather effects (lightning storm everyone takes damage if lightning hits them, foggy - chance to miss, etc). Tiles that do different things (slows movement, gives +1 damage while on the panel, damages you every other turn, fog of war).  Fog of war (enemies can't see you inside tall grass - like League of Legends or Brawlstars).