In terms of mind-expanding or intellectually stimulating, I find it's easier to get that from Youtube. I recommend: 3blue1brown for math (https://www.youtube.c

In terms of mind-expanding or intellectually stimulating, I find it's easier to get that from Youtube. I recommend: 3blue1brown for math (https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw) Everyday Astronaut if you are casually interested in rockets (https://www.youtube.com/channel/UC6uKrU_WqJ1R2HMTY3LIx5Q https://www.youtube.com/channel/UC6uKrU_WqJ1R2HMTY3LIx5Q) Bret Victor (https://www.youtube.com/watch?v=PUv66718DII&list=PLS4RYH2XfpAmswi1WDU6lwwggruEZrlPH https://www.youtube.com/watch?v=PUv66718DII&list=PLS4RYH2Xfp...) or Rich Hickey (https://www.youtube.com/watch?v=f84n5oFoZBc&list=PLXsqD83He-e5oUh_DFrHbO3MoNj3tG8Vh https://www.youtube.com/watch?v=f84n5oFoZBc&list=PLXsqD83He-...) for programming and design. Doing a full college course is such a time investment and it usually takes a few weeks to start proving the interesting stuff. I find it more fun to look to shorter content for inspiration. I might realize I don't understand the fundamentals of the topic and then seek out a way to study it.