SPICE
SPICE is a general-purpose, open-source analog electronic circuit simulator. It stands for Simulation Program with Integrated Circuit Emphasis. ngspice is a successor, and is easily installable on Linux. It’s the simulator I’ve used to explore the Skywater 130 PDK.
Here’s an example spice simulation file that I used to simulate the inverter I drew.
And here’s a nice demo of me showing how a flip-flop works by simulating a Sky130 D type flip flop with SPICE.
Course feedback
Don't think twice about taking this course, It uses a unique method, you get to do stuff yourself and learn by playing around. Getting through this course and designing my own ASICs was the greatest experience of my life.