.io games are only entertaining because they are massively multiplayer, when you remove the dependence of other players to play the game, the game will always loose value as the game play is always about multiplayer interaction and not anything else, i can tell this game was worked on constantly and has a lot of love put into it, to make it an io game is pointless, you should have just made a defensive game with the same art-style, spawning waves and create progression not fixed game play. There's potential yes, but it needs more work.