Agreement and license
These terms apply to Plain Chess and related services from Cerebra Enterprises LLC ("we", "us", or "our"). By using the app, you agree to these terms. The app is licensed under Apple’s Standard End User License Agreement: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/. These service terms supplement that license and do not limit rights you have under applicable consumer law.
Plans at a glance
Plain Chess is free to download. Prices below are in US dollars; the App Store shows your local price, currency, and billing period before you buy.
- Free ("Daily Chess"): one new game a day and the daily puzzle, at no cost.
- Plain Chess Coach membership: Plain Chess Annual at $39.99 per year, with a 7-day free trial for eligible new members; Plain Chess Monthly at $4.99 per month; or Plain Chess Family at $69.99 per year for up to six people.
- Plain Chess Lifetime: $99 once, for everything in the membership except AI Coach answers.
- AI Coach answer packs: 25 answers for $2.99, 75 for $7.99, or 250 for $19.99.
We may change which plans and offers the app shows. A plan you already bought keeps working as these terms describe.
The free plan
The free plan includes one new game a day in any mode: against one of our rivals, with a friend, through Quick Match, or pass and play on one iPhone. A rematch counts as a new game. A game already in progress, such as a daily game with a friend, keeps going. You also get the daily puzzle, and one hint and one threat check in that day’s game. After each game you see your accuracy; the moments to learn from, full game reviews, opening lessons, voices and AI Coach are part of the membership. Your games are saved, and joining unlocks your whole history. The day’s allowance resets at midnight in your iPhone’s time zone. We may change the free plan’s limits; the app always shows the current ones, and they never apply to a paid plan.
Plain Chess Coach membership
The membership includes unlimited games in every mode, unlimited hints and threat checks, a review of every game, your full game history (synced through your own iCloud when you are signed in), every puzzle and opening lesson, the voice coach and rival voices, asking the coach out loud, and 300 AI Coach answers a month. Plain Chess Annual is billed $39.99 once a year, about $3.33 a month. Plain Chess Monthly is billed $4.99 each month. Plain Chess Family is billed $69.99 once a year and is shared through Apple’s Family Sharing, as described under Family.
Free trial
New members may be offered a 7-day free trial of Plain Chess Annual. Apple decides who is eligible and offers a free trial once per Apple Account, so you may not be offered one if you have subscribed before. When a trial is offered, the app and the App Store purchase offer show its length and the price charged after it. You are not charged during the trial. If you allow notifications, Plain Chess reminds you two days before the trial ends. Unless you cancel at least 24 hours before the trial ends, the plan’s price is charged when the trial ends and the membership then renews as described below.
Renewal and cancellation
Payment is charged to your Apple Account when you confirm purchase. A membership renews automatically unless you cancel at least 24 hours before the end of the current billing period. Your account is charged for renewal within 24 hours before that period ends, at the renewal price shown in your Apple Account. Manage or cancel your membership in Apple Account settings. Cancellation stops future renewals; access normally continues until the paid period ends, unless Apple refunds or revokes it. Deleting the app does not cancel a membership.
Changing plans
You can switch between Plain Chess Annual, Monthly and Family in your Apple Account’s subscription settings, and the App Store handles the change. Moving up to Family starts right away, and Apple refunds the unused part of your current plan. Moving from Family to Annual or Monthly, or between Annual and Monthly, takes effect at your next renewal date. The plan you move to is billed at the price the App Store shows when you switch. Answers from packs stay yours when you switch.
Founding members
If your yearly or monthly membership started before July 17, 2027, including a free trial that started before then and turns into a paid membership, you are a founding member, and your membership keeps its price for as long as it stays active. You also get the full membership described above, including 300 AI Coach answers a month. If you switch to a different plan or your membership ends, that price is no longer guaranteed; the App Store shows the price before you subscribe again.
As a thank-you, founding yearly members get 120 AI Coach answers once, added when Apple confirms a paid year of that membership. They join your pack answers and, like them, do not expire.
Already bought Plain Chess?
If you bought Plain Chess when it was a paid download, you keep the gameplay you bought, with no subscription and no daily limits: every game, puzzle, review, hint and lesson. The app verifies that earlier purchase through Apple; use Restore Purchases with the Apple Account you used to buy it if access is missing. Earlier ownership does not include monthly AI Coach answers. You can buy answer packs to ask the AI Coach, or choose to subscribe. Subscription terms apply only when you choose a subscription.
Plain Chess Lifetime
Plain Chess Lifetime is a one-time purchase, $99 in the US, offered at a founder’s price for a limited time. We may stop offering it or change its price at any time; a Lifetime you already bought is not affected. It includes everything in the membership except AI Coach answers, for as long as Plain Chess is offered. It does not renew, so there is nothing to cancel. Lifetime owners can buy answer packs to ask the AI Coach, typed or out loud. Lifetime belongs to the Apple Account that bought it, is not shared through Family Sharing, and can be restored with Restore Purchases.
AI Coach answers
Each successful AI Coach reply uses one answer, including follow-up questions and questions you ask out loud. Members get 300 answers a month. Unused monthly answers expire when the next month’s answers arrive; they do not roll over. Monthly answers are used first, then answers from packs. Lifetime owners and original buyers have no monthly answers and can use packs. The free plan does not include AI Coach. To use any answers, including answers from packs, you need a membership, Lifetime or the original paid app; answers you bought stay on your coach account if your membership ends, ready when you have a paid plan again. If AI Coach cannot produce a reply, for example because the service is busy, the question does not use an answer.
Family
Plain Chess Family is shared through Apple’s Family Sharing with up to five other members of your family group, so up to six people can use it, each with their own Apple Account. Everyone sharing it gets the full membership, and the family shares one pool of 300 AI Coach answers a month. If Apple’s purchase information does not let us group a family’s members together, each person sharing the membership gets 50 AI Coach answers a month instead. Who shares the membership is managed in Apple’s Family Sharing settings. Answer packs are not shared: each person’s packs are their own. Plain Chess Lifetime is not shared through Family Sharing.
Answer packs
Answer packs are consumable purchases: 25 AI Coach answers for $2.99, 75 for $7.99, or 250 for $19.99 in the US. They are offered to Lifetime owners, original buyers, and members who have used their monthly answers; they are not offered on the free plan. Pack answers do not expire, are used after your monthly answers, have no cash value, and cannot be transferred, sold, or exchanged for money. Apple’s Restore Purchases does not restore consumable purchases, so our billing service keeps your pack balance with your coach account token, which reaches your other devices through iCloud; contact support if a purchased balance is missing. AI credits bought before Plain Chess 2.0 keep working: each credit is one answer.
Interrupted AI answers
If an answer is interrupted, the app can recover the same reply without using another answer. Closing the coach or putting the app in the background does not immediately return the answer. Delivery is confirmed only after the reply is saved on your device. If a completed reply has no delivery confirmation seven days after the original request, a monthly answer is returned to the month it came from, up to ten a month; an answer from a pack is not returned this way. A monthly answer keeps its original expiry; one returned after its month has ended does not add an answer to a later month.
Fair use of AI Coach
AI Coach is for your own chess questions. Monthly answers are for the person or family whose plan it is. Do not share access outside your family, send questions with scripts or other automated tools, resell answers, or try to get around answer limits or other usage safeguards. AI Coach answers chess questions and briefly redirects questions that are not about chess. To keep the service working for everyone, we may limit how many questions come from one connection in a short time, and we may pause AI Coach for a coach account or purchase used in these ways. AI Coach requires an internet connection.
Our rivals and games with other people
Our rivals, Pip, Fern, Ivan, Maya, Orion, and Nova, are AI opponents with written personalities. They are never people. Play a friend and Quick Match use Apple’s Game Center, and Game Center’s terms also apply. Quick Match looks for a person near your level; if nobody is found within about 10 seconds, you play one of our rivals instead, labeled "AI rival". There is no chat in games with people; you can send six preset reactions. Please play fair: do not use another app or another person to choose your moves, and do not harass other players.
AI Coach and practice goals
AI Coach is optional. With your agreement, your chess position and question are sent to our backend and AI provider. Answers can be incomplete or wrong and are for general learning and entertainment. Do not submit personal or sensitive information. Practice goals and commitments are choices you make for yourself. They are not promises to us, purchase obligations, or conditions for receiving paid features. You can change your goals. We do not guarantee a particular chess rating or improvement.
Billing help and refunds
Apple handles payment processing and membership management. You can request a refund through https://reportaproblem.apple.com, subject to Apple’s policies and your applicable rights. For access or answer problems, contact corporate@cerebraenterprises.com. We may adjust answers or access when Apple refunds or revokes a transaction.
Fair use and availability
Do not use Plain Chess unlawfully, interfere with our services, bypass purchase or usage safeguards, or infringe others’ rights. Restrictions on reverse engineering apply only to the extent allowed by law. We may update or temporarily suspend services for maintenance, security, or legal reasons. Online features may be unavailable at times. If we materially change or discontinue a paid service, we will provide any notice, remedy, or refund required by law and Apple’s applicable policies.
Ownership and responsibility
Plain Chess, its design, branding, and content belong to Cerebra Enterprises LLC or its licensors. To the extent permitted by law, services are provided as available, without a guarantee of uninterrupted service or error-free AI output. We are not liable for indirect or consequential loss to the extent the law allows this limitation. Nothing in these terms excludes liability or consumer rights that cannot lawfully be excluded.
Open source notices
Arasan Chess Engine
Copyright 1994-2026 by Jon Dart
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Puzzle and opening data
Puzzles come from the Lichess puzzle database (https://database.lichess.org/#puzzles) and opening names from lichess-org/chess-openings (https://github.com/lichess-org/chess-openings). Both are dedicated to the public domain under Creative Commons CC0 1.0.
Coach and rival voices
The natural voices are computer-generated speech, made on your iPhone with open source software and a speech model: kokoro-ios (MIT, Copyright (c) 2025 Lassi Maksimainen), a port of MLX Audio (MIT, Copyright (c) 2024 Prince Canuma); MisakiSwift and MLXUtilsLibrary (Apache License 2.0, Lassi Maksimainen and contributors), with pronunciation dictionaries from misaki (Apache License 2.0, hexgrad) and a fallback model by Peter Reid (Apache License 2.0); swift-npy (MIT, Copyright (c) 2020 Qoncept, Inc.); ZIPFoundation (MIT, Copyright (c) 2017-2025 Thomas Zoechling); MLX Swift, MLX and MLX C (MIT, Copyright (c) 2023 ml-explore and Copyright © 2023 Apple Inc.), with PocketFFT (BSD 3-Clause, Max-Planck-Society and others), metal-cpp (Apache License 2.0, Apple Inc.), JSON for Modern C++ (MIT, Niels Lohmann) and {fmt} (MIT, Victor Zverovich and contributors); Swift Numerics (Apache License 2.0, Apple Inc.); and the Kokoro-82M speech model and voices (Apache License 2.0, hexgrad; the model in mlx-community’s conversion for MLX, its weights rounded to bfloat16 by Plain Chess), whose architecture is StyleTTS 2 (MIT, Copyright (c) 2023 Aaron (Yinghao) Li) and whose training audio included Koniwa (CC BY 3.0) and SIWIS (CC BY 4.0). The full notices and license texts are in the app under Settings, Legal, Acknowledgements.
Privacy, changes, and contact
Our Privacy Policy explains information handling: https://cerebraenterprises.com/plain-chess/privacy. We will update the effective date when these terms change. Cerebra Enterprises LLC, 5000 Thayer Center Ste C, Oakland, MD 21550. Email: corporate@cerebraenterprises.com.