Hello! Glad you enjoyed the game. Was our first project so glad to get something playable out there.
To answer your question;
You do finish the level by jumping off the bridge, probably should have made that clearer.. oops!
After you lower the drawbridge a next level trigger spawns underneath it.
So once you roll off the drawbridge, it should take you to the next of 4 levels.
Again, thank you for your kind words!