Charged Detonation

You charge up a huge amount of energy and cause yourself to blow up, dealing 2d6 lighting damage to both you and everyone within a 15ft radius. You can take an action to either charge the spell or cast the spell. The spell can have up to 4 charges before it overloads. The spell will not be canceled if you are hit. Each charge increases the damage by 1d6 and the radius is increased by 5ft, maxing out at 6d6 and 35ft. All creatures within range must make a strength saving throw of 10 + your strength modifier. Each creature is pushed to the edge of the spell's radius and takes full damage on a failed save. On a successful save, they take half damage and are pushed half as far. If the spell over loads, it will deal one extra d6, and cause the ground to turn into rough terrain. Any allies that would be hit are unaffected by the spell. You can cast this spell again after a long rest.