A brilliant, blue-white beam of lightning flashes forth from your fingertips, forming a line 100 feet long and 5 feet wide in a direction you choose.   You can cause the beam to bounce once off of a solid, nonconductive object that you can see (such as a stone wall) in a new direction you choose equal to the beam’s remaining length. Each creature in the beam's path must make a Dexterity saving throw. A target creature takes 4d12 lightning damage on a failure, or half as much damage on a success.   The lightning ignites flammable objects in the area that aren't being worn or carried.