As of 20170311a3_2, two sparkly objects appear when you try to cast to show you where your hands have to go for the current spell.
For multi-part spells (the fireball for example) they will repeat each part a few time then go on to the next one, and then start again.

The speed at which they move is good for casting. You can move faster but you don't have to and your precision might suffer.

If you can create the initial firelight but can not shoot the fireball, check where where they are in the second part of their pattern, which starts after three revolution.
By the way, casting is always relative to your orientation (but NOT by the inclination of your head!)

I hope this will solve most magic-related problems.

CHANGELOG :
20170311a3_2:
added magic guides while casting
added vibration while casting
fixed spell lighting
tweaked the wumpus attack distance