This post was originally published in 2012 on the Startup Grind blog, I'm republishing and expanding it here.

Lots of startups just don't seem to get it. They focus on things that don't matter instead of on the most important piece of the startup puzzle: the core mechanic. But what's a core mechanic? Well, I'm glad you asked. The core mechanic is what makes your product novel and exciting to your users. It's checkins for Foursquare, search for Google, and photo filters for Instagram (2014 observation, it's also talking to doctors on First Opinion). Basically, the core mechanic is the main reason someone who isn't your mom will bother to use your product.

Most Startup founders go wrong because they think a novel core mechanic is just an additional feature on top of an existing mechanic, it's not. If your pitch includes the phrase, "product x with a twist" then stop right now and go back to the drawing board. Just because an existing product doesn't have a feature you want doesn't mean you can build a successful business by cloning the product and adding that feature, and even if you did gain some traction, you'll almost certainly play second fiddle to the product you copied because they pioneered the original mechanic to begin with.

Why is a core mechanic so important? Because it will be your most powerful sales tool. That's exactly what happened to me the first time I saw an iPod touch in the Apple store. 30 seconds with it and I knew I had to have one, the core mechanic (in this case, the user experience) was so good I disregarded any limitations I knew it had, in fact, I didn't care about its limitations at all because everything else about it was so good. That's the kind of product every entrepreneur should want to make, but few actually do. You'll know you're on to something when people start nodding in agreement as you describe your product because it offers them something they want.

Once you've got the right core mechanic then your users will be hooked. Twitter was forgiven during the fail-whale years because Twitter was so addictive that people couldn't stay away; Finally, instead of only whispering your awesomely funny and insanely witty comment to the person sitting next to you during a boring presentation, you could broadcast your genius to the whole world. Likewise, if you've got a great core mechanic, your users will forgive missing features and product missteps because of the value they do receive when they use your product.

The tricky thing about a core mechanic is it's only novel and revolutionary once. Those who follow your trailblazing footsteps will have diminishing returns. Groupon owns the daily deals space because they found a core mechanic that resonated with people (2014 observation: too bad Groupon's hook doesn't make actual money, zing!). However, all those Groupon clones that quickly popped up and tried to capitalize on Groupon's success are dropping like flies because what Groupon offered was no longer enough. Personally, I think daily deals sites are like auction sites. Can you name an eBay competitor? Exactly! Yet, I remember in the late nineties you couldn't mistype a url without stumbling on a brand new auction site.

So what should your startup focus on? Most definitely the core mechanic. Nothing else really matters. You can have the slickest designed product in the world but it doesn't matter if you don't have the right core mechanic. A great example of this is Path, their first version was widely regarded as one of the most beautiful iOS apps anyone had ever seen, yet no one used it. It wasn't until Path fixed their core mechanic problems that people began to care (2014 disclaimer: I have since worked at Path, and it was awesome).

Your core mechanic is your app, site, or product's total value proposition. If you don't have a good core mechanic, you don't have anything. When you do finally have a great core mechanic, every time you think of adding a feature, ask yourself, does this feature accentuate my core mechanic? If it doesn't, resist adding it.

But don't just take my word for it, take Alan Cooper's word from The Inmates are Running the Asylum:

Programmers will naturally emphasize edge cases, but they can largely be ignored during the product's design. This doesn't mean that the function can be omitted from the program, but it does mean that the interaction needed for them can be designed roughly and pushed way into the background of the interface ... the product will succeed or fail in its ability to handle daily use and necessary cases. ...

If a user performs a task frequently, its interaction must be well crafted. Likewise, if a task is necessary but performed infrequently, its interaction, although designed with different objectives, must still be well designed. Tasks that are neither necessary nor frequent simply don't require careful design. Time and money are never available in unlimited quantities, so this is the place to conserve our resources safely and concentrate them where they do the most good. ... we need to design only for those that are important or that will occur frequently.

Core mechanics also have different sized markets, some products are novel and great, to a small subset of people, that's exactly what we found out at Plancast (last 2014 observation: sigh).

Supplementary Material

Skype is a perfect example of nailing the core mechanic, via Ars Technica:

Talking to a computer felt silly at the time—as silly as talking to your hand did when mobile phones first appeared. Feedback on the initial version of Skype was not exactly enthusiastic. The sound was glitchy, for instance. But when testers realized that they could now speak via computer to people on the other side of the world for free, attitudes changes