Challenges
Design Principles
Difficulty Tiers
One-Time Price
How It Works
Three simple steps to sharpen your design eye. No setup, no prerequisites.
Pick a Challenge
Choose from 12 design principles like contrast, hierarchy, and spacing. Start at Beginner and work your way up to Expert.
Spot the Difference
You'll see two nearly identical UI designs side by side. One follows best practices, one doesn't. Can you tell which is which?
Build Your Instinct
With each challenge, you train your eye to catch what most people miss. Over time, good design decisions become second nature.
Why I Built This
After 10+ years reviewing designs, from junior portfolios to product teams, I kept seeing the same patterns. Designers understood design theory but struggled with design decisions. They could explain what good contrast was, but couldn't spot bad contrast in a real UI.
The problem? There was no place to practice. You could read about typography hierarchy all day, but there was nothing that forced you to actually see it, judge it, and train your eye on it. The way a musician trains their ear.
So I built SpotTheUI. 480 real A/B comparisons, organized by principle and difficulty, designed to turn design knowledge into design instinct. No fluff. Just reps.
Ruben Cespedes
Principal Product Designer & Design Educator
Ruben has spent over a decade designing products and mentoring designers. He's passionate about making design education practical, accessible, and actually fun. SpotTheUI is the training tool he wished existed when he was starting out.
What Designers Say
Early feedback from the design community
“I've taken expensive design courses but nothing trained my eye like this. The A/B format is genius. It forces you to actually look instead of passively consuming.”
Sarah K.
UI Designer
“Perfect for junior designers on my team. I have them do 10 challenges a day as warm-up. Their attention to detail improved noticeably within weeks.”
Marcus T.
Design Lead
“The Expert tier is no joke. Even with 8 years of experience, some of those challenges had me second-guessing myself. That's when you know it's actually working.”
Priya R.
Senior Product Designer