Write Python or JavaScript, press run, and watch execution stream into a living graph. Scrub a timeline to replay any moment — deterministically — down to the variable.
Edit Python or JavaScript/TypeScript in a focused editor. One run opens a stream — no setup, no build step, no login.
Each value, call and collection becomes a node. Data flows in on cyan, execution flows out on amber.
Drag the timeline and the whole surface rebuilds at that exact step — graph, console and variables in lockstep.
1def fibonacci(n):2 seq = [0, 1]3 while len(seq) < n:4 seq.append(seq[-1] + seq[-2])5 return seq67numbers = fibonacci(8)8total = sum(numbers)
Follow control as it moves — calls, branches and loops trace themselves across the graph as amber execution edges.
Every variable, in every scope, at every step. Collections show their deltas: what was appended, sorted, removed.
The timeline is the source of truth. Rewind to any step and the entire surface is rebuilt exactly as it was.
The Free plan needs no card — 5 JavaScript runs a day, resets daily. Paid plans add Python & TypeScript, longer runs, and more, each starting with a 7-day Pro trial (cancel anytime). Billed in INR via Razorpay; students at partner colleges get a free first month, then ₹10/mo.
Student plan is for verified students at allowlisted colleges — eligibility is automatic once you sign in with your institutional email (no extra steps). Not listed? Ask us to add your college.