Hey thanks for your feedbacks, I'm setting the limit to position units at most 70% of the bridge, so the enemy can "wind up" before facing too many ally units. I think this is not obvious for players.
And the target of the game is to defend, not destroying enemy's base so to win the level you just need to level up until max and defeat their dragon.
I hope this is clear to you and welcome any feedback as the game subjects to change