FOR MANY DESIGNERS, UI design goes something like this.

Map out basic experience flow in OmniGraffle, Sketch, Illustrator, etc. Make lots of sketches mocking up how the interface could work, usually on paper Take pictures and transfer to computer, scan and send to oneself, and sometimes spread out on desk for reference Design wireframes in Illustrator, Sketch, etc. (often with UI kits) Design high-fidelity mockups in Sketch, Adobe XD, Photoshop, etc. Import screens into a prototyping tool to simulate interactivity and navigation, such as InVision, Flinto, Marvel, Proto.io, etc. Test the experience with users Iterate on design based on user feedback

Many designers actually start on 4 or 5 (you know who you are). But even if a designer goes through all these steps, notice how much time and effort you have to invest before you get to something you can test and learn from! And there’s another problem: this is a very linear process. Interactive product experiences aren’t linear or static, and you can’t design for them that way either.

People typically prototype in low fidelity with markers on paper to keep the exploration cost low and focus feedback on the desirability or essential effectiveness of the solution. People usually prototype in high fidelity to hash out the details once they’ve nailed down the basic approach, and test it out in real-world conditions. But with modern design and prototyping tools being what they are, interactivity often comes last. The problem is the in-between: for interactive media, how do you figure out if you’re on the right track, before investing in the hard work of getting the details right?

Right now, that only exists in a messy combination of tools. But what if you had something in between — the speed and convenience of sketching and iterating on a tablet, with the real-time feedback loops of interactive prototyping tools?

The workflow hack

That’s the tool I wanted. So I figured out a little hack, using Paper and Marvel, to prototype an app idea (basically a UI flow mapping tool based on Ryan Singer’s shorthand, targeted at UX designers and content strategists). I know, I prototyped a designer tool by prototyping another designer tool. Meta.

My idea for a UI flow mapping tool.

First, I sketched some screens.

Well this is a annoying.

Without bothering with high fidelity yet, I wanted to see how the experience would feel. So I exported the screens from Paper, imported them into Marvel, and quickly created hotspots to link the screens together. In a few minutes, I had this:

The idea here is a tool that would allow designers to quickly flesh out “what the user sees” and “what the user does” for each step, creating a map of a UI flow in the process.

With my sketches suddenly interactive, I could already get a sense for whether this kind of interface would work, and what I’ll need to design for when I get into the details.

It works, but barely. I love Paper’s speed and elegance, but it’s pretty annoying to Share > Save to Camera Roll > Switch to Marvel > Import from Camera Roll > Create Hotspots every time I want to try out an idea (I discovered you can export directly to Marvel, but there are still several steps involved).

As it turns out, Marvel has a sketching feature built in, but it clearly wasn’t the focus, and the drawing tools are underdeveloped and mostly unusable. Still, in about 10 minutes I made a rough prototype of an Apple Watch app concept to help people more conveniently connect on LinkedIn when they meet in person.

Again, it’s pretty crude, but very quickly I have a sense for whether this experience will work, and what kinds of interactions I’ll need to design for.

The Game-Changer

IF THE LOW-FIDELITY SKETCHING and iterating on a single device (with the ease and elegance of something like Paper) and the ability to add link screens with hotspots for real-time testing could exist in a single app, that would be game-changing.

You’d get a near-instant feedback loop, and leap forward in your ability to quickly flesh out an idea to see if it makes sense. Add some tools like Paper’s smart shapes (ones that work consistently), and maybe some built-in UI kits, and iPads would become a must-have designer tool.

Crucially, this is what would make an iPad genuinely better than a sketchpad (easy iteration in a single place, with interactive functionality) and better than a MacBook (rapidly sketch and test ideas without the burden of high-fidelity).

The pieces already exist; they just haven’t come together yet.

Paper is as effortless as sketching on a real notepad, with a great start to the (sometimes erratic) smart shapes, but without any kind of prototyping features, it’s a workflow hack rather than a true solution. Marvel already has drawing tools in their prototyping app, but it seems obvious that feature hasn’t been a focus so far, and there are enough accumulated oddities in the UI to make it frustrating. Adobe Comp seems very promising (especially with its gesture-based smart shapes, as well as typically excellent Adobe smart guides), but it’s hard to make a collection of individual screens as part of a concept, and you still have to go through the export process to another tool before you can test an idea. In my view, it also veers too far into high-fidelity for the earliest stages of design; when you want that kind of control, Sketch or XD is faster and better. What we need is something with the bare-minimum simplicity and conceptual focus of a sketchpad—just start drawing—but with basic interactive prototyping functions.

Could someone make it happen soon? I think so. FiftyThree? Flinto? InVision? Proto.io? Adobe? Marvel? Do that and you will be the hero of UX/UI/product designers — and the justifier of iPad Pro line items on expense reports everywhere.