FREE
1. Array Plains
Scanning, reversing, prefix sums, rotation, Kadane
Write real code. Watch it come alive.
Code the Hero turns data structures and algorithms into a pixel adventure. You write JavaScript, press Run, and a hero walks, lifts, swaps, stacks and searches — exactly as your code says, one highlighted line at a time.
No sign-up. Works on phones and laptops. Your progress saves in your browser.
How it works
Every level is one small coding task set in a pixel world — the kind of problem you meet in placement tests and interviews.
1
Write code
Every level starts with partly written code. Tap command chips to type fast on a phone.
2
Press Run
The hero acts out each command while the running line lights up, so you see how the algorithm works.
3
Earn stars
Your code is also tested on hidden inputs. Efficient solutions — the right Big-O — earn three stars.
// Level 1.1: find the heaviest crate let best = crates.get(0); for (let i = 1; i < crates.length; i++) { let w = crates.get(i); // hero lifts crate i if (w > best) best = w; } submit(best); // ★★★ one lift per crate
Mistakes become enemies
- Off-By-One Impappears when you reach past the end of a row.
- Infinite Looperspins when a loop never stops.
- Null Wraithhaunts you for popping an empty stack.
- Lag Goblinsswarm code that repeats work.
Each one comes with a plain-language hint on how to fix your code.
10 worlds · 70 levels
The core interview syllabus in learning order. Each world ends with a boss.
FREE
2. Twin Rivers
Two pointers and sliding windows
FREE
3. Hash Harbor
Hash maps, two sum, anagrams, prefix sums
PREMIUM
4. Binary Peaks
Binary search and searching on the answer
PREMIUM
5. Sorting Factory
Selection, insertion, merge and quick sort
PREMIUM
6. Mirror Caves
Recursion, backtracking, N-Queens
PREMIUM
7. Chain Railway
Linked lists and Floyd's cycle detection
PREMIUM
8. Stack Tower
Stacks, queues, monotonic stacks, deques
PREMIUM
9. Tree Forest
Traversals, binary search trees, heaps
PREMIUM
10. Graph Kingdom
DFS, BFS, topological sort, union-find, Dijkstra
Made for
Students
Preparing for campus placements and coding rounds, on a budget phone or a laptop.
Developers
Switching jobs and brushing up on patterns and Big-O in short sessions.
Beginners
Know a little code and want DSA to finally click, with starter code in every level.
Free to start
FREE
Worlds 1–3 · 21 levels
- Arrays, two pointers, sliding windows and hashing
- Streaks, badges and hero outfits
- No ads, ever
PREMIUM · COMING SOON
All 10 worlds · 70 levels
- Binary search, sorting, recursion, linked lists, stacks, trees and graphs
- Daily challenge leaderboard
- Solution replays and exclusive outfits
Planned from ₹149 a month, ₹999 a year or ₹1,999 once.
Questions
Do I need to install anything?
No. The game runs in your browser on phones, tablets and laptops. On a phone you can also add it to your home screen, and it keeps working offline.
Which programming language?
JavaScript. Python is planned for a later update.
Is my code really run?
Yes. Your code runs in a safe sandbox inside your browser. Every command it calls is recorded and acted out by the hero, then your code is checked on hidden inputs so it has to truly work.
Where is my progress saved?
In this browser, on this device. Accounts with cloud save across devices are coming soon.
Is there an Android app?
An Android app is on the way. The web version is the same game.
Ready, hero?
King Brute broke the world with slow, clumsy code. Only you can fix it.
▶ Start Level 1