Hanging in the studio with my friend Kian

From Biting Nails to Building Mac Apps With the Power of GPT-4

Obie Fernandez


My good friend Kian Pak never imagined he would create a Mac app, let alone one that could spark an evolution in his career. For years, Kian struggled with a bad habit that plagued him day and night — nail biting. He tried everything to kick the habit, but nothing seemed to work. That is until one day, he had an epiphany.

Most of the time, Kian caught himself biting his nails while working on his computer. At some point, years ago, that he realized he could take advantage of the technology he was using to help break his habit. With his background in front-end software development, Kian had the idea to create an app that used Apple’s neural engines to detect when he was biting his nails and intervene.

Kian: I wanted to make a Mac app but I had no fucking idea, like, where to even start, right? I opened up XCode and it was, like, super confusing.

I didn’t know Swift. I didn’t know all the Mac OS APIs. I didn’t understand how to make a native interface. My day job, I’m just using HTML and CSS.

So I just kind of, like, let that idea sit for years.

Obie: And there’s nothing else like this? That you know about, wow!

Kian: I did look for it and hoped somebody else would do it.

Obie: So then GPT comes around?

Kian: Yeah. And I thought, oh, well, I’m pretty sure Apple has, like, some neural engines that does, like that does computer vision, hand tracking, facial feature tracking. I thought, well, duh, I can make an app that uses the webcam that’s already always looking at you. And if you, you know, if it catches you biting your nails, then it does something to make you stop.

Obie: How did you come up with the mechanic of it would do? Was that, like, as soon as you started developing or did take some iterations?

Kian: Yeah. I had a few different ideas at first. Maybe that it would, like, charge you money. Another idea was that would make a noise. I like the noise idea, but ended up just going with the full screen overlay because like, you could be working in a coffee shop and have this go off without, you know, embarrassing yourself. If it made noise then you would not be able to use it in the office, right?

Obie: The money thing seems unrealistic, really.

Kian: Yeah. At the time, I didn’t do the money thing because it was, like, more complicated. But now that I’ve been using the app, I like the way it works just fine.

Obie: I need an app like this for picking my nose!

Kian: Yeah I mean, that could be done because the nose is a facial landmark. Apple’s computer vision can detect all the landmarks on the face and all the joints of the fingers. For Hands Down I just told it to to track for 10 fingertips and what Apple has defined as the inner lip of the mouth.

Obie: Wow.

Kian described his vision to GPT-4, and it gave him step-by-step instructions to create the app. When Kian didn’t understand certain elements of the process, he asked GPT-4 to make comparisons to the programming language he was familiar with. The AI model provided the code, and Kian had his app.

I asked him to tell me more about how that went down.

Kian: I was using GPT-3.5 for a couple months when the big hype wave started at the end of 2022 and it blew my mind. But it was still making enough mistakes that I was like, yeah, this is not really going to be good enough.

But when GPT-4 came out, I was like, oh shit! This could actually guide me all the way through.

Obie: Be good enough for what, though?

Kian: Good enough to get me all the way through, you know? Like from start to finish, basically. GPT 3.5 could get you started with like a new Rails ew rails app, for example. Just it would just give you conventional generators and stuff.

But once I got kind of further into the project, I felt like it was kind of, like, losing track of itself and starting to make shit up because his his memory wasn’t long enough. But, anyway, I found that GPT-4 fixed all that. And and what do you actually ask GPT-4 at the beginning of this project? Like, how do I create a Mac app? Is it that simple?

Yeah. I told it I told it, hey, I want to create a Mac app that uses the webcam to to track, you know, the users’ fingers and there and and maybe throw up a a full screen overlay when they when it catches them, put anything else near their mouth. What do you think? Like, is that even possible? What do you think?

Should do. Because I didn’t even know it was, like, possible. It would not let you throw up a a full screen overlay and stuff like that. Or would they let you run the the webcam constantly. If you don’t have, you know, like like a video chat app or something like that, like, in the background.

Obie: So, you get the project off the ground by describing exactly what you want to do to GPT-4, right? And then it starts giving you instructions? And then when it tells you something that you don’t know how to do because you’ve never done Swift programming before, then what?

A picture of the app in action!

Kian: It pretty much spit out a long list of things I had no idea what they meant or how to do. And it gave me a step-by-step list full of things that I wasn’t familiar with. So I told it: “hey, I’m a Rails developer. If you can make comparisons to Rails for me to help me understand this, that would be cool.

Obie: And did it do that?

Kian: It did at the start, yeah!

Obie: So wait, was this all in one conversation?

Kian: Yeah. It was one long conversation.

Obie: Really?

Kian: It’s a super long conversation! I definitely hit the [GPT4 usage] limits, and like was forced to take breaks.

But basically, I just told it, okay, let’s get started with step 1 because it had already outlined the whole thing. And it fleshed out what that would entail. And then I said, okay, “Give me the code.”

And GPT essentially said: Open up Xcode, open up a new file, name it this, and here is the code.

Obie: Wow! So, start to finish. How long did this all take?

Kian: I would say it took about two days of actual work to get it working for me, and that blew my mind. And then it took one more day to spruce it up for release with settings and a bunch of other details. The longest part of the process was just getting approval from Apple to let me distribute the app!

Obie: Did it help you with that as well?

Kian: It did, yeah! I was trying to figure out how I can distribute a Mac app without using the App Store, but in the end, I decided to just sell it on my website instead.

Obie: So did you get any feedback from users? How has the reception been?

Kian: The reception has been surprisingly positive. I wasn’t expecting much, considering it’s a pretty niche app that solves a specific problem. But I’ve gotten a lot of feedback from people saying it’s helped them break their nail-biting habit. Some people have requested additional features, like the ability to track other habits or add custom alerts.

And there have been some requests for improvements, like making the app more accurate in detecting when someone is actually biting their nails. But overall, the response has been really encouraging. It’s been a great experience to see something I built helping others with the same issue I had.

Obie: So, do you think you would have been able to create this app without the help of GPT-4?

Kian: Absolutely not. GPT-4 was like having a mentor or a teacher guiding me through the process, which made it so much easier and more enjoyable. It allowed me to learn by telling me exactly what to do instead of trying to interpret potentially irrelevant Youtube videos, or having to rely on the terrible Swift documentation.

Obie: Well, that’s an amazing story, and it’s incredible to see how far AI has come in assisting with tasks like this. I think it’s really going to let a lot more people express their creativity through software!

Hands Down is a Mac app designed for people who bite their nails. The app uses the computer’s webcam to track the user’s fingers and detect when they’re biting their nails. If the app catches the user biting their nails, it displays a full-screen overlay to intervene. I’m promoting it here simply because Kian is a personal friend, and I think this is an awesome story about how GPT-4 is empowering people to do things that they didn’t think they could do before. I don’t have any personal financial interest in the project or promoting it.

Hands Down is available for $29 on Kian’s website, but you can get it for 40% off with the discount code 93PYQ4O35K.



Obie Fernandez

CEO of RCRDSHP, Published Author, and Software Engineer. Chief Consultant at MagmaLabs. Electronic Music Producer/DJ. Dad. ❤️‍🔥Mexico City ❤️‍🔥 LatinX (he/him