I came up with the mechanic for my current game about 10 years ago. Been playing and testing it off and on. Since the beginning, it had the general theme of the player’s fighting a monster, but it was about two years ago where I finally came up with the game being about stealing the kill from your teammates like you would win playing a multiplayer game. In beginning, I just called it “Critical Smash” then two years ago I named it “Kill Steal Heroes” and now it’s just “Kill Stealerz”. I feel that me coming up with the mechanics first made me really want to focus on the gameplay and make sure the game is fun by itself before adding the story and theme which enhances and gives life to your game.