DailyDiff (“每日一辨”) is a focused English vocabulary app built around a single daily puzzle. Each day you get a pair of easily confused words — like Begin vs Start — each with a black-and-white line illustration. You write, in English, how the two words differ in meaning, tone, and usage; an AI scores your answer and reveals a model answer.

Four steps:

1. See today’s word pair and its two illustrations.
2. Explain the difference in English.
3. Get AI feedback across five dimensions, plus the model answer.
4. Keep your daily streak and, if you like, share a no-spoiler result card.

No. You can start playing right away as an anonymous user — no email, no password. Sign in with Apple is optional. Signing in gives you a larger daily scoring allowance and syncs your history across devices. Studying and answering past puzzles is a Pro feature — and since subscriptions are tied to your Apple account, signing in is the first step.

DailyDiff is an iOS app for iPhone. It requires an internet connection because the daily puzzle, illustrations, and AI scoring are all delivered from our server.

This is the heart of DailyDiff — and what makes it more than a quiz. Your answer is read and evaluated on five dimensions, each from 0 to 100, and every dimension comes with its own written comment:

• Accuracy — is the distinction you describe correct?
• Coverage — did you capture the key differences?
• Language — grammar, word choice, and fluency.
• Clarity — how clearly the explanation reads.
• Insight — depth, nuance, and good examples.

The comments aren’t canned templates — they’re written for your exact answer, pointing out what you nailed and what you missed, like a one-on-one tutor reading your work. That personalized feedback is where the real learning happens, far beyond a single number.

The dimension scores roll up into a total and an overall grade — from D up to S, plus the rare SS and SSS reserved for near-flawless answers with no weak dimension — shown with a radar chart, a short summary, and the model answer to compare against.

Write your answer in English. DailyDiff is an English-learning app, and the scoring rewards a clear, accurate explanation written in English. A few words is rarely enough — aim for one or two well-formed sentences.

Scoring looks at more than whether you’re “not wrong.” A correct but very short or vague answer may lose points on coverage, clarity, or insight. Compare your answer with the model answer shown after scoring — it highlights the nuances worth mentioning.

The AI does its best, but it isn’t perfect. If you believe a score is clearly off, we’d love to hear about it at support@dailydiff.vip.

Complete the puzzle each day to extend your streak, Wordle-style. Miss a day and the streak resets. Your calendar fills in as you go, so you can see your progress at a glance.

You can always re-open puzzles you’ve already completed and review your answer, score, and the model answer. Studying or attempting earlier puzzles you missed is a Pro feature. Future puzzles are never available early — everyone gets the same puzzle on the same day.

No. The share card shows only the word pair, the illustrations, your grade, a radar chart, and a short summary. It deliberately leaves out the model answer so your friends can still play.

Playing a new puzzle needs an internet connection. However, puzzles you’ve already completed — including their illustrations — are cached on your device, so you can review your past results offline.

Pro raises your daily AI-scoring allowance, lets you study and attempt past puzzles you missed, and includes upcoming Pro-only features. The daily puzzle and core scoring remain free for everyone.

Pro is an auto-renewing subscription offered as a monthly or yearly plan. The exact price for your region is shown on the subscription screen in the app and confirmed by Apple before any charge. Payment is handled by your Apple account.

Subscriptions are managed by Apple, not inside the app. On your iPhone, open Settings → [your name] → Subscriptions → DailyDiff to change plans or cancel. If you cancel, you keep Pro until the end of the current billing period.

Sign in with the same Apple ID you used to subscribe, then use “Restore Purchases” on the subscription screen. Signing in with Apple also brings back your puzzle history.

We receive an opaque Apple user identifier (and a relay email only if you choose to share one). We never receive your Apple password or payment details. See our Privacy Policy for the full picture.

In the app, go to Profile → Delete Account. This permanently removes your server-side account and associated records. Deleting the app also clears the history stored on your device.

Note: deleting your account does not cancel an active subscription — only you can do that, in iOS Settings → [your name] → Subscriptions. Cancel there first if you don’t want to keep being charged.

The text you submit is sent to our backend and to third-party AI service providers solely to generate your score and feedback. We don’t sell your data or use your answers to advertise to you. Details are in our Privacy Policy.

AI scoring has a real cost, so anonymous play includes a small free daily allowance. Signing in raises it, and Pro raises it further. The limits also help prevent automated abuse so the service stays fast and reliable for everyone.

To curb abuse, we cap how many brand-new anonymous devices can appear from a single network each day. On a shared Wi-Fi (an office or school) you may hit this cap. Signing in with Apple bypasses it instantly and is the recommended fix.

Email support@dailydiff.vip — we read every message. Including your device model and iOS version helps us help you faster.