I need to make the skill bar interact with a launch button and make it one shot, also change the mouse pointer for a cross until the skill has been launched, the interaction would be all with the mouse.
I’m not really sure what you mean by “make the skill bar interact with a launch button and make it one shot” but see here for the mouse part.
the skill system would be like this:
1- The user selects the skill
2- the user presses a button to cast spell
3- the user clicks on another user and the spell is cast
and every time you want to cast a spell you must repeat this sequence