The best professional simulation tool ever Have been using it my entire carrier (25 years by now). Fortunately, it is free of charge, after it has been (unfortunately) discontinued. So for private tasks with elderly parts still a great tool. For newest parts, probably LT spice will be necessary-
Best Spice tool I have used in the last 2 decades. If you have a question, look at the help, or Help, Demos. Lots of great things. NFV are great, they are Analog behavioral voltage source that allow you to write your own equations, they can be very complex and time or frequency dependent.