Thanks for playing! Glad you liked it!

I am sure how I did it is not the best way, but it was the only way I thought of doing it.
Here is a quick explanation for how I went about doing it:

When you Hit left click it starts collecting the location of the mouse and getting the average value. This average value is essentially the middle of the circle, as the average of points on the edge of a circle should be the middle of the circle. This list of locations is reset if the player:
a) Lets go of the mouse
b) Goes in the opposite direction
c) A full circle is created
It also keeps track of the direction from the first value(Location of mouse when you hit left click) to the average value calculated earlier. 
Then it checks 4 things
a) Their have been more then 10 locations tracked
b) The current angle of the mouse to the average is near the angle from the first position to the average.
c) Are their 3 points in the circle that differ from the first position by at least 90 degrees

d) Are these 3 points far enough away from the center.

If all of these things are true then it counts it as a circle having been completed and the list is reset.

This is frankly a finicky system but for a game jam it tracked circles well enough.

Glad you liked the idea. I think your right, maybe halve the enemies on the first level...or remove that level when it is not the tutorial.

Thank you! I don't think its a skill issue, I think the system could use some work. If I had more time, or maybe I will add it after the jam I would prob add some system to 'cheat' aiming a bit, where if you are close, you instead just hit.

Thanks for playing! Yeah its kinda a finicky system, I thought that process was gonna be a lot easier! Essentially. to charge you have to hold left click and spin somewhat tightly and quickly then when you are charged enough you release while moving in the direction you want to throw your lightning.