I used an HP RPM calculator through college. It could do cool stuff like graphing and solving equations. Very helpful for an engineering student, not so helpful later in life. I used that calculator until about a year ago when it died (got about 35 years from it). I didn’t use the super fancy stuff anymore, but for a scientific calculator it was pretty solid.

So when it broke, I had to find a replacement for a device that I’ve used for my entire life. Needless to say, I was kind of picky. I tried emulators, and newer TIs, and only one made me happy. A silly little iOS app “PCalc” (it has an icon of “42”). It was like $5, runs on my phone, and honestly I probably should have switched decades ago.

I’m not associated with that app or the author or anything, just a recommendation for anyone old and stubborn like me - I know I’m not alone here with calculator attachment issues :)