Frequently Asked Questions

What is Differdle?

Differdle is a free calculus practice game. Each session gives you a stream of derivative and integral problems. Solve them correctly to build your score — answer one wrong and your run ends. Your best score goes to the global leaderboard.

Think of it like a speed-run through a calculus problem set, except you're competing against students from around the world instead of just your classmates.

Who is Differdle for?

Anyone studying calculus — AP Calculus AB or BC, Calc I and II in college, or anyone who just wants to keep their skills sharp. The Easy difficulty covers fundamentals suitable for students just starting derivatives; Hard covers multi-step composite problems that will challenge students mid-way through Calc II.

Is Differdle free?

Yes, completely free. No paywall, no subscription, no feature gating. Creating an account is optional — it just lets you save your score to the leaderboard and track your stats over time.

Can I use Differdle on my phone?

Yes. The site is designed to work on mobile, tablet, and desktop. The math input keyboard adapts for touch screens. Some complex expressions may be easier to enter on a physical keyboard, but all problems are fully solvable on mobile.

How does scoring work?

Each correct answer adds points based on the difficulty you selected:

• Easy: 1 point per correct answer
• Medium: 3 points per correct answer
• Hard: 5 points per correct answer

The moment you answer incorrectly, your current score is submitted to the leaderboard and your counter resets to zero. There's no limit to how long a run can go — the highest run ever recorded is your "best score" on the leaderboard.

Does my score only save if I get one wrong?

Your score saves to the leaderboard when your run ends — either because you got a problem wrong or because you manually clicked "New Problem" mid-run (which also ends the run). If you close the tab mid-run, the score is not saved. Only your best-ever score appears on the leaderboard; a lower score on a new run won't replace it.

What is "Lifetime Score"?

Your Lifetime Score (visible on your profile) is the cumulative total of all points you have ever earned across all runs, not just your best single run. It's a measure of total effort and consistency, whereas your leaderboard score is your single-session peak.

Can I mix difficulty levels within a run?

No — you choose a difficulty before your run starts and it stays fixed for that session. This keeps the scoring fair: a 10-point score on Hard represents a very different level of effort from a 10-point score on Easy.

What does each difficulty level cover?

• Easy: Single-rule problems. Power rule, basic trig derivatives (sin, cos), and simple exponentials with no chain rule required. Ideal if you're just starting derivatives or warming up.
• Medium: Multi-rule problems. Chain rule, product and quotient rules, logarithms, and combinations of the above. This covers the bulk of AP Calculus AB and Calc I material.
• Hard: Composite and nested problems. Multiple chain rules, integration by parts, mixed trig identities, and problems that require correctly identifying and applying 2–3 rules in sequence. Corresponds roughly to Calc II difficulty.

What do the Topic buttons (Poly, Trig, Log, Mix) do?

• Poly: Problems focus on polynomial and algebraic expressions — power rule, roots, fractional exponents.
• Trig: Problems involve trigonometric functions — sin, cos, tan and their derivatives, including chain rule applications with trig.
• Log: Problems involve logarithmic and exponential functions — natural log, e^x, and their combinations.
• Mix: A random blend of all three topics. This is the most realistic exam preparation mode since actual calc exams don't tell you which rule to use.

Recommended: Practice each topic individually first to identify weak spots, then switch to Mix mode before exams.

What's the difference between Derivatives and Integrals mode?

The toggle at the top of the game switches the entire problem set between differentiation and integration. Derivatives mode asks you to find f′(x); Integrals mode asks you to find the antiderivative. The difficulty and topic selections apply to both modes.

How do streaks work?

Your streak counts how many consecutive days you have played at least one problem on Differdle. Play today → streak increases by 1. Miss a day entirely → streak resets to 1 on your next visit. Your all-time maximum streak is saved separately and is never reset.

Streaks are tracked per calendar day, not per 24-hour window. Playing at 11:55 PM and then again at 12:05 AM counts as two separate days.

What is "Accuracy" on my profile?

Accuracy is the percentage of problems you have answered correctly out of all problems you have attempted. It is a cumulative lifetime stat — it does not reset between sessions. A high accuracy with a high lifetime score is the sign of someone who is both consistent and careful.

How does the leaderboard work?

The leaderboard shows the top 5 players by their best single-session score. "All Time" shows the highest score ever achieved by each player. "7 Days" and "24 Hours" filters show only scores earned in that time window, ranked highest first — useful if the all-time leaderboard is dominated by a few veteran players.

Why don't I see my score on the leaderboard after a run?

The leaderboard only updates if your new score is higher than your existing best. If you scored 12 points today but your all-time best is 20, the leaderboard won't change — 20 stays as your entry. Your new score does still count toward your Lifetime Score.

Can I click on other players' profiles?

Yes — clicking any row on the leaderboard opens that player's public profile card, showing their rank, streak, lifetime score, and accuracy. Only information they've made public by playing on the leaderboard is visible.

Do I need an account to play?

No. You can practice indefinitely without an account. Creating one just lets you save your score to the leaderboard and track your personal stats (streak, lifetime score, accuracy) between sessions.

How do I delete my account or data?

Email us at westbrook.alistair@gmail.com with the subject "Account Deletion Request" and include the email address or display name associated with your account. We will remove all your data within 30 days, in line with our Privacy Policy.

I found a problem with an incorrect answer. What should I do?

Our math engine validates answers symbolically, but edge cases can exist — especially with equivalent forms of the same expression (e.g. 2x·cos(x²) vs 2x*cos(x^2)). If you believe you entered a correct answer and it was marked wrong, please contact us with the function and the answer you entered. We review every report.