Master coding interviews with bite-sized practice.
Bugl turns algorithms, data structures, and system design into short, game-like sessions across 7 languages — with real code execution, visual explanations, and timed mock interviews.
No credit card. No install. Start solving in seconds.
function containsDuplicate(nums) {
const seen = new Set();
for (const n of nums) {
if (seen.has(n)) return true;
seen.add(n);
}
return false;
}⏱ Time
O(n)
💾 Space
O(n)
3036+
Problems
18
Patterns
7
Languages
Practice questions asked at companies like
Everything you need to go from practice to offer
One place for the daily reps, the deep understanding, and the interview rehearsal.
Bite-sized puzzles
Fill-the-blank, trace, spot-the-bug, and optimal-solution challenges that build real intuition, not rote memorization.
Real code execution
Run solutions and see them pass tests — JavaScript and Python execute live right in your browser, no setup.
Visual walkthroughs
Watch arrays, hash maps, trees, and graphs animate step by step so the algorithm actually clicks.
Use-case system design
Design a URL shortener, news feed, and rate limiter step by step — requirements, capacity, architecture, and tradeoffs.
Company paths
Curated study plans and company-tagged lists so you practice exactly what your target companies ask.
Mock interviews
Premium: timed 1-1 rounds, weakness tracking, and prep tuned to the role and company you’re targeting.
How Bugl works
A guided path, not an endless problem list.
Pick your goal & language
Tell us whether you’re prepping for interviews, learning a language, or studying system design. We default puzzles to your language — switch anytime.
Practice in focused sessions
Short daily puzzles, guided lessons, and system-design walkthroughs keep a streak going without burning you out.
Track weaknesses & rehearse
See which patterns lag, drill them, then rehearse under the clock with timed mock-interview rounds.
Many ways to practice one problem
Every problem becomes multiple puzzle modes, so you read, write, debug, and optimize — not just recall.
Design real systems, step by step
Start with the building blocks, then work through canonical interview systems with guided decisions and an interactive architecture board.
URL Shortener
Hashing, base62, read amplification, caching
News Feed
Fan-out on write vs. read, timeline materialization
Rate Limiter
Token bucket, sliding window, distributed counters
Rehearse the real interview
Live 1-1 mock interviews with timed rounds, weakness tracking across every session, and prep tuned to your target companies and role.
- Timed coding, system design & behavioral rounds
- Weakness analytics that target your practice
- Company- and role-specific question sets
Frequently asked questions
Is Bugl free?+
Yes — all puzzles, learn tracks, and the system design track are free. Premium adds live 1-1 mock interviews and weakness analytics.
Which languages are supported?+
JavaScript, Python, TypeScript, Java, C++, Go, and Rust. JavaScript and Python run live in your browser; the others are checked against reference solutions.
Do I need to install anything or create an account?+
No. Bugl runs entirely in the browser with no setup, and you can start solving without an account. Sign in to sync your streak and progress across devices.
Is this for beginners or for interview prep?+
Both. The onboarding questionnaire tailors difficulty — from your very first puzzle through interview-grade practice and timed mock rounds.
Ready to solve your first Bugl?
Pick a goal and a language, and we’ll build a path that fits the time you have.
Get started