I design apps that millions of people love using every day

While others obsess over pixels, I obsess over what happens when things go wrong and how to simplify the chaos, because that's where real design earns trust.

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SJ

Redesigning Sweden's Most-Used Travel App

• Experience

SkiStar

A Ski resort app, or several. SkiStar is the largest ski resort brand in Scandinavia with 5 resorts. I've redesigned the app from top to bottom.

• Experience

PostNord

Porto-codes are a part of the PostNord APP where users can buy digital stamps for sending letters

• Experience

I'm Gustav

I’ve spent the last few years at a product-focused design agency tackling the complex stuff that doesn’t make it into portfolios.

System migrations, edge cases, business logic, internal politics. That's where design really makes a difference – and that's where I thrive.

For SJ, I led the App design of a complete ticketing system migration, one of the largest IT projects in Sweden that year, while millions were still using the app every week. I rebuilt the purchase flow, established the new design system, and aligned UX across app, web, and external resellers. At the same time, I built a house, moved cities, and became a dad again. Turns out, both app design and house design benefit from a strong foundation and a clear sense of what matters.

What I bring is calm, structure, and an ability to get people pulling in the same direction – even in messy situations. I design solutions that last, with both business and minds.

Latest Projects

E-mail

[email protected]

Download CV

Swedish:

CV-Gustav-Mårtensson-2025.pdf

English:

CV-Gustav-Mårtensson-2025-EN.pdf

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How I led the redesign of Sweden's most used travel app

Designing under pressure: when failure isn't an option and millions of Swedes trust your work to get them home

1m+

Montly Travellers

3 600

Meetings

400+

Decisions

20+

User Tests

1 Experience

Across 3 Platforms

2021

The Challenge

When I joined the SJ app project, it was a mess. The design lived in scattered Sketch files, had no proper design system, and was built on an outdated ticket system that was about to be completely replaced.

It wasn't just redesigning an app - it was rebuilding the entire digital backbone that millions of Swedes depend on daily, while keeping the old system running until the new one was ready.

My role
& approach

As lead designer, I didn't just push pixels. I became the bridge between three different teams:

My job was translating a web-focused design system into something that actually worked for app, while keeping both platforms feeling cohesive.

The Process

A) Building the Foundation

First, I migrated everything from chaotic Sketch files to a structured Figma system, creating app-specific components that honored both iOS/Android guidelines AND SJ's new brand direction.

B) Redesigning Core Flows

We rebuilt every single flow from scratch, testing with real users throughout. Some wins:

C) Managing the Transition

The trickiest part? Launching while keeping the old system running. We had to prioritize ruthlessly - some features got cut, others got merged. Every decision was tested and validated with user data.

Key Solutions

The Period Card Revolution

Problem:
Period tickets were buried and confusing.Solution:
Created a prominent card at the top of tickets view.Impact:
70% easier to find and use.

Real-time Travel Mode

Problem:
Existing travel mode lacked visual journey tracking and lacked proper guidance up on train changes.Solution:
Added live map with real-time position tracking, improved transitions, and restructured traffic info.Impact:
Users can now visually follow their journey in real-time, reducing anxiety and customer service calls about delays and other traffic information questions.

Results & impact

Launched on time despite being Sweden's largest IT project that year. While some users missed certain features initially, the app has been widely praised for being cleaner, faster, and more intuitive.

What I learned

Leading a project this complex taught me that good design isn't just about making things pretty - it's about managing constraints, building bridges between teams, and never losing sight of the millions of real people who depend on your work.

Personally? It taught me to stop second-guessing myself and start trusting that I'm the designer in the room for a reason.

Try it out

How I transformed Sweden's largest ski resort app from outdated to award-worthy

1 year, complete visual overhaul, app store rating from 2.8 → 4.1

The Breif

SkiStar needed their app ready for a new ski season with fresh features. In my role as UI Designer, I saw an opportunity to do more than just add functionality - I gave the entire experience a complete visual makeover.

The Airbnb app at the time became the main inspiration.

Premium
and playful

I used their beautiful slope maps as the foundation for a new illustration style that feels both premium and playful.

Adding the Mountain for each destination made it both functional and beautiful - Instead of just reading 'Åre' or 'Sälen', users could instantly identify their resort while feeling the excitement of the mountain experience.

Profile
with stats

Redesigned the entire profile experience around a stunning lift station illustration

Users can now seamlessly connect their ski cards to track rides, compare vertical meters with friends, and see their mountain achievements come to life through clean data visualization and gamified leaderboards.

Impact

The redesign wasn't just about looking good - it was about creating an app that skiers actually love using. From 2.8 to 4.1 stars some years later proves that great UI design directly impacts user satisfaction.

Try it out

How we guided 2+ million travelers through a booking system migration without losing their trust

When SJ needed to run two booking systems simultaneously, clear UX design became the difference between chaos and calm.

The Crisis

SJ was replacing their entire booking backbone while keeping millions of monthly bookings flowing. For months, we'd run two systems in parallel - old trips in the legacy system, new trips in the updated one. Users booking travel could land in either system depending on their dates, and we needed to make this technical nightmare feel intentional and clear.

The stakes were high: any confusion could mean lost revenue, frustrated travelers, and overwhelmed customer service. SJ wanted the simplest possible solution - no expensive technical bridges, just smart UX and clear communication.

The challenge in numbers:

The Breakthrough

Working with a skilled iOS developer who understood the technical constraints, I developed an approach that could work for both app and web. The key insight: stop trying to hide the complexity and instead guide users through it clearly.

Move the calendar first

Instead of routing users invisibly, we moved date selection to the very beginning with an upfront message about the system transition. This let us direct users to the right booking flow immediately based on their travel dates.

Design honest empty states

When users navigated to unsupported dates, we created empty states that clearly explained how to find trips - guiding them back to adjust their search rather than hitting confusing dead ends.

The Hardest Part: Edge Cases

The real challenge was handling the impossible scenarios: rebooking old tickets for new system dates, return trips that spanned both systems. We had to be brutally honest - users would need to cancel and rebook separately.

Getting the copy right

We ran 4 user tests focused purely on these edge case messages. Our first version had an 'info' button explaining the system change, but users clicked it expecting to move forward and hit a dead end. We removed it and refined the copy until users intuitively understood they needed to go back and recalibrate.

Leading
the Solution

I took the lead in presenting our approach to SJ's web team and stakeholders, who adopted our strategy across platforms. This wasn't just a design challenge - it required convincing stakeholders that our UX-focused solutions would maintain users trust in the service during this period.

The politics were intense, but we proved that clear communication and smart routing could solve what seemed like an impossible technical problem.

Results & Victory

An incredible victory - we turned what could have been a customer service nightmare into a smooth, barely-noticed transition.

What I Learned

This project taught me that sometimes the best design solution isn't hiding complexity - it's being honest about it while making users feel guided and safe. Leading cross-platform UX strategy showed me how mobile-first thinking can drive solutions across entire ecosystems.

Redesigning SJ's timetable for everyone - including 40% with enlarged text

Balancing accessibility, information hierarchy, and conversion for millions of daily searches

The Accessibility Challenge

SJ's existing timetable worked for some users, but failed millions of others. The design system's new beautiful cards hid crucial pricing information, while the old table-based layout couldn't scale text without losing all hierarchy.When 40% of your users have enlarged text settings, and screen readers can't parse your content logically, you have a problem that goes beyond aesthetics.

The challenge:

Research
& Discovery

We ran 2-3 user tests to understand both the existing experience and design system variants. Combined with web analytics from their earlier release, we saw clear patterns: users needed pricing transparency and better overview without sacrificing accessibility.

We partnered with an external accessibility agency for a thorough audit, identifying specific barriers in both design and function. The biggest insight: beautiful doesn't mean usable if people can't actually use it.

Two Views,
One Experience

Instead of forcing one solution, we created two complementary views:

Card view

Rich information with train illustrations for each departure type, perfect when you need detail and context.

List view

Minimal height per departure, maximum overview, scales perfectly to 2x text size while maintaining clear hierarchy.

Smart pricing menu:

Choose your preferred class and see those prices across all departures - no more clicking through to compare first-class fares.

Accessibility-first Design Decisions

Key features:

Testing
& Iteration

Results
& Impact

What I Learned

We user-tested our redesigned timetable 3 times, refining copy and information hierarchy based on real user behavior. The external accessibility audit helped us catch edge cases we'd missed.

Launch strategy:

We defaulted to card view initially, but quickly noticed users preferred the list view for its superior overview. We switched list to default with smooth transitions to cards when users needed more detail.

Trade-off honesty:

Some users miss seeing all prices at once, but the majority appreciate the cleaner, more accessible experience.

This project taught me that inclusive design isn't about adding accessibility features later - it's about making accessibility the foundation of every design decision.When you design for the most constrained users first, you create better experiences for everyone

SkiStar

A Ski resort app, or several. SkiStar is the largest ski resort brand in Scandinavia with 5 resorts. I've redesigned the app from top to bottom.

• Experience

How digital keys transformed SkiStar's check-in from stressful to seamless

3 weeks to design, endless relief for families arriving late with tired kids

The Family
Nightmare

Picture this: You've driven hours to your ski holiday. The kids are tired, it's getting dark, and you need to find some reception office, join a queue with everyone else who just arrived, get instructions, then drive around looking for your cabin. Miss the office hours? Hunt for a key box somewhere.

SkiStar knew this was broken.
The solution: digital locks and app-based keys that let families skip all that and go straight to their cabin.

The challenge:

As UI designer, I got a UX brief and a few days to make this work. The technical challenge was designing for two different lock types:

Users needed to understand the difference and feel confident they could actually unlock their door.

Design Solutions

Key features:

Visual: Screenshots showing the two lock types and animations

Making it
Foolprooof

The animations weren't just pretty - they were essential instructions. When you're standing outside your cabin in the cold, you need to instantly understand whether to hold your phone up to the door or just tap the unlock button.

We also planned for the inevitable tech failures. If your phone dies or the digital lock stops working, there's always a physical key at the cabin as backup - so you're never locked out in the snow.

We validated the entire flow with on-site testing by SkiStar staff in Sälen to make sure it worked in real conditions.

What I learned

Sometimes the biggest design wins come from solving the smallest, most annoying problems. Three weeks of design work eliminated years of family stress.

This project also taught me Lottie animations - turns out they're perfect for UI that needs to be both instructional and interactive. When done right, animation isn't decoration, it's communication.

PostNord

Porto-codes are a part of the PostNord APP where users can buy digital stamps for sending letters

• Experience

How we turned a 12-character code into a simple alternative to physical stamps

Making PostNord's digital stamps feel effortless, not confusing

The Complexity Challenge

PostNord wanted to let people buy stamps digitally instead of hunting for a store. Simple idea, complex execution.Users needed to write a 12-character code in a very specific format (XXXX XXXX XXXX stacked vertically) on their envelope, plus additional text for priority mail and country codes for international letters.

Get the format wrong, and your letter won't be processed. Make the instructions too long, and people will just walk to the nearest store instead.

The challenge:

The Solution

Created visual step-by-step guides showing exactly how to write codes on actual envelope illustrations. Added a "My Digital Stamps" management list (missing from original brief) to track active/used stamps.

Key features:

Result

Successfully launched without user confusion complaints - a major win for such a complex feature.

Learning:

Sometimes the most important design work is identifying what's missing from the original brief.