Codee
A coding-test practice platform for job seekers. Instant AI feedback, three problems a day, and a growing character bring fun and motivation to self-directed study.
Impact
- Introduced an adaptive feedback system that reduced early-stage dropout by 15% and increased average session duration.
- Implemented level-adjusted feedback and reward structures that strengthened learners’ sense of progress and improved mission completion rates by 20%.
- Enhanced motivation and weekly re-engagement through optimized reward timing and gamification loops, contributing to a double-digit increase in return activity.
Role
Product Designer (UX 80% · UI 80%)
Timeline
Feb – Apr 2024 (2 Months)
Team
1 Product Designer · 1 Backend Dev · 1 Product Manager · 1 Frontend Dev
Tools
Figma · Blender · Procreate · Illustrator · Photoshop
Contribution
As the product designer, I led the end-to-end UX of an adaptive learning and coding-practice app.
- Designed reward and task flows that reduce cognitive burden and support repeated practice.
- Conducted user interviews and analyzed behavioral patterns to optimize feedback timing and difficulty scaling.
- Built a lightweight design system and character graphics suited to rapid iteration across web and mobile.
01
Overview
What if a coding test came with AI feedback?
I had been using AI in my design work and wanted to apply it to a project of my own and launch a user-friendly product. At LIKELION, I collaborated with aspiring developers to plan a platform called Codee.
On existing coding-test platforms it is hard to get real-time feedback while solving problems. Codee provides instant AI feedback, a feature other platforms lack, and explores ways to make coding more enjoyable. The goal was to bring fun and motivation even to self-directed learning.
02
Problem & Solution
Common challenges among job seekers preparing for developer positions
Our Rocket Lion team analyzed the difficulties job seekers face while studying coding. Based on LIKELION's core value, "Making coding accessible to everyone," we planned a platform for people preparing to enter development. The UX focuses on habit formation, gamification, and AI-powered solutions to boost motivation and engagement.
Problems
- Motivation ↓
- Feedback ↓
- Habits ↓
Solution
- AIInstant AI feedback
- HABITThree problems a day to build a habit
- GAMECharacter-growth gamification
03
Solutions
The proposed solutions map one-to-one onto the UX as three features: AI feedback, three daily challenges, and character growth, so users naturally immerse themselves in the platform.
01
AI feedback
Provides AI-generated answers with detailed explanations and personalized feedback on the user's own code.
02
Three problems a day
Recommends three coding problems per day to help users build a consistent problem-solving habit.
03
Character growth
Levels up a character with points earned from solving problems, keeping learners engaged and motivated.
04
Graphic System
I chose a cat as the main character because its traits, nocturnal and fond of staying indoors, align well with a developer's lifestyle. The character, named Codee, short for "Coding Cat," combines this idea with pixel-style graphics inspired by the nostalgic games loved by millennials and Gen Z.
Logo · App icon
Button states
05
UI Component System
We built a component-based design system for consistency, efficiency, and scalability across the service. Since the target users are in their 20s to 30s, the system evokes nostalgia by referencing the pixel games they enjoyed as children.
Color
Primary
- Dark green#44B044
- Normal#32CD32
- Point#00E46C
Secondary
- Normal#192E47
- Light#27466B
Dark mode
- Background#17171B
- Section default#32323A
- Section feedback#3F3F47
Basic
- Black#222222
- White#FFFFFF
System
- Positive#398FF5
- Negative#F53966
Gray scale
- 900#363738
- 800#454545
- 700#545454
- 600#777777
- 500#8B8B8B
- 400#989898
- 300#BDBDBD
- 200#DBDBDB
- 100#EAEAEA
- 50#F4F4F4
Typography · Pretendard
- Headline 1Coding tests made easy for beginners32 · Bold · 130%
- Headline 2Coding tests made easy for beginners28 · Bold · 122%
- Title 1Coding tests made easy for beginners20 · Medium · 100%
- Pixel Text 1Coding tests made easy for beginners20 · Medium · 100%
- Title 2Coding tests made easy for beginners16 · Medium · 156%
- Title 3Coding tests made easy for beginners14 · Regular · 120%
- Pixel Text 2Coding tests made easy for beginners14 · Regular · 120%
- Title 4Coding tests made easy for beginners12 · Regular · 120%
Chips · Tabs · Calendar
06
UI Flow
Today's coding test
At Codee, AI generates three new problems every day to help users build a consistent coding habit. Each successful solution earns a "check-in stamp," so users can visually track their progress and achievements.
AI code comparison and bookmarks
Users identify issues in their code and receive feedback by comparing it side by side with AI-generated solutions. Code can be saved as bookmarks, and the responsive design lets users review it anytime, anywhere.
07
Responsive UI
Based on user feedback (VOC), a responsive UI was designed so users can review their code anytime, anywhere. Coding itself is not available on mobile because of the interface, but users can still revisit and review the problems they have solved.
08
Results
Two weeks after launch, Codee reached 223 sign-ups, including 80 active users. Based on user feedback and VODs, we developed an English version and added new programming languages. Codee was later featured as the #1 trending project on velog, a well-known developer community blog.
223
Sign-ups within two weeks of launch
80
Active users
#1
Trending project on velog
- 01Codee launch
- 02English version, Java support, responsive web version
- 03223 sign-ups and 80 active users in two weeks, featured on velog Trends
What's next
Future goal
Achieve 1,000 active users by Q3 2026
Focus
Strengthen community engagement through user-generated content
velog
Maintain continuous, feedback-driven product iterations