The heart of game development lies in the unplanned, the unexpected. 
Something accidental, a peculiarity, spawned by the game may be a sign your game wants to live.

Now, your game is creating itself.

Now your game has a heart.

Many choose not to let their game thrive, they sacrfice the game's heart for their own initial plan, idea, logic, comparing with other games Wanting to use other game's logic.

But you cannot plan a game's heart.