Terms of Service | csmasters.dev

1. Operator & Acceptance

csmasters.dev (“the Service”) is operated by Artem Blazhievskii, an individual based in the Philippines (“we”, “us”, or “our”). By accessing or using the Service, you agree to be bound by these Terms of Service. If you do not agree, you must not access or use the Service.

2. Eligibility

The Service is available to individuals aged 13 years or older. You must declare your age band during registration. We do not knowingly accept registrations from individuals under 13. If we learn that a user is under 13, we will promptly delete their account and data.

Learners aged 13–17 may use the free tier independently. Upgrading to paid All-Access requires guardian authorization (see Section 5).

3. Accounts & Security

Each person may maintain one account. You are responsible for maintaining the confidentiality of your password and for all activities that occur under your account. Do not share your credentials with others. Notify us immediately at [email protected] if you suspect unauthorized access.

4. Free Tier & Paid All-Access

The Service offers a free tier and paid All-Access as a subscription or fixed-duration pass:

Free tier includes:

Reading theory lessons across all modules and tracks
Interactive exercise practice within Module 1 only, including autotests and trace tables
Standalone pseudocode workspace (compiler and sandbox)
Streaks, XP, badges, and progress tracking

All-Access adds:

Full interactive exercise practice across all modules and tracks
AI Tutor — a conversational study assistant (see Section 7)

5. Guardian Responsibilities

Learners under 18 require explicit guardian authorization before purchasing or using paid All-Access. A parent or legal guardian must review and confirm the upgrade request, including acknowledging the AI Tutor processing notice, via a secure email link.

Guardians may revoke their authorization at any time using the secure revocation link provided in the confirmation email. Revocation immediately disables AI Tutor access and blocks new checkout. It does not itself cancel an existing Lemon Squeezy subscription; the purchaser must request cancellation separately. Guardians are responsible for monitoring their child’s use of the Service.

6. Billing, Renewal, Cancellation & Refunds

All payments are processed by Lemon Squeezy, which acts as our Merchant of Record. Lemon Squeezy handles billing, tax calculation, and remittance across jurisdictions. We do not process or store credit card numbers or full billing details.

All-Access is available for one, six, or twelve months. At checkout, the purchaser selects either an auto-renewing subscription or a one-time pass. The subscription renews at the selected interval unless cancelled. A pass has no recurring charge and expires automatically. Additional paid pass time extends the existing pass expiry. One active subscription is allowed per learner. A pass cannot be bought during active subscription access, and a subscription cannot start until an active pass expires.

Adult purchasers can turn off auto-renewal in Account Settings. Guardians receive a secure billing link. Cancellation stops future renewal charges and preserves access until the paid-through date supplied by Lemon Squeezy, unless access has ended because of a refund. Cancellation does not itself refund an earlier payment or restore refunded access. Renewal cancellation remains available after a refund and covers all known renewing subscriptions. One-time passes require no cancellation.

Refund Policy & 14-day money-back guarantee

Your first purchase

We offer a 14-day money-back guarantee on the first successful paid All-Access purchase for each learner: a one-, six- or twelve-month one-time pass or the first payment of an auto-renewing subscription. Email [email protected] within that period and we will refund that payment in full. You do not need to give a reason. Using lessons, exercises or the AI Tutor does not disqualify you. A parent or guardian who paid for the learner may request the refund. Free Preview use does not count as a paid purchase.

The deadline is exactly 14 calendar days (336 hours) after the successful payment timestamp in the Lemon Squeezy payment record. A request received at the deadline qualifies. For example, payment at 10:00 UTC on 1 October has a deadline of 10:00 UTC on 15 October. The time we receive your email determines eligibility, even if we process it later. Renewals, additional passes and repeat purchases do not restart the guarantee, including after a previous refund or a change of payer.

Six- and twelve-month purchases outside the guarantee

For a six- or twelve-month payment that is not eligible for the first-purchase guarantee, you may request a refund calculated as: amount paid for access − ($30 USD × full elapsed months), with a minimum of $0. This applies to one-time passes and six- or twelve-month subscription payments, including renewals. We use the actual access price after discounts, excluding tax, and deduct each completed month at the standard $30 USD monthly rate.

For refund calculations, one month means 30 consecutive calendar days. Each day is a consecutive 24-hour period, measured in UTC. Only completed 30-day periods count; an incomplete period is not charged and is not prorated by day. Divide elapsed days by 30 and round down. Calendar-month boundaries do not affect this calculation.

Elapsed access runs from the start of the period funded by that payment until we receive your request, capped at the end of that period. Access counts while it is available, whether or not you log in. An additional pass queued behind an existing pass begins counting when its own access period starts, rather than when you pay. We round the final refund to the nearest cent, deduct any access-price refund already issued for that payment and cap the result at zero. You will never owe an additional payment under this calculation.

For example, before tax and prior refunds, a six-month purchase for $79 has a $79 refund after 20 days, a $49 refund after 30 days, and a $0 refund after 90 days. This values elapsed access at the monthly rate, so the refundable balance may reach zero before the discounted access period ends.

One-month payments outside the first-purchase guarantee do not qualify for a refund under this voluntary policy. We will still review duplicate charges, payment errors and claims under applicable law.

Requesting and receiving a refund

Email [email protected] with the learner’s account email and the Lemon Squeezy Order ID or renewal invoice reference. If you cannot find the reference, send your purchaser email and payment date so we can help locate it. Missing information does not change your original request date; we may ask for enough information to verify the payment and your authority to request a refund.

We aim to review requests within five business days (Monday to Friday). We will confirm the outcome and explain any partial-refund calculation. Approved refunds are issued through Lemon Squeezy to the original payment method. Once issued, a refund may take up to ten days to appear on your statement, depending on your payment provider.

For a full refund, you receive the amount actually charged, including applicable tax, less any amount already refunded. We do not deduct processing or administration fees. For a partial refund, Lemon Squeezy handles any corresponding tax adjustment. Our prices and refund calculation are in USD. Lemon Squeezy processes payments in USD even when checkout displays another currency. Your bank’s exchange rates or fees may affect the amount shown in your local currency.

Access and automatic renewal after a refund

Any refund, whether full or partial, immediately ends the learner’s All-Access entitlement held at the refund time. The access expiration is set to the refund timestamp recorded by Lemon Squeezy, rather than the original paid-through date. Existing stacked passes or earlier purchases are not automatically restored after a refund. A new paid purchase made after that timestamp can grant fresh access; delayed notification of an earlier refund does not cancel that later purchase. Access continues while a request is being reviewed; sending a request alone does not revoke access.

If you request a refund of a subscription payment, we will also turn off future automatic renewal and confirm cancellation. You can cancel renewal separately without requesting a refund. Cancellation alone does not refund an earlier payment and preserves any remaining unrefunded access through its paid-through date.

Your consumer rights

This voluntary policy is additional to your statutory consumer rights. It does not limit any right to withdraw, obtain a refund or seek another remedy under applicable law, including for a faulty or misdescribed service or an unauthorized charge. Where the law provides greater protection, that protection applies.

7. AI Tutor — Limitations & Disclaimer

The AI Tutor is an All-Access feature that provides Socratic teaching guidance. It is powered by OpenAI and is designed to help you learn — not to provide direct answers.

The AI Tutor is not a replacement for a qualified teacher, tutor, or examiner. Its responses may contain inaccuracies.
We set store: false so OpenAI does not store application state for later retrieval through the API.
Separate OpenAI abuse-monitoring logs may retain API inputs for up to 30 days.
We filter detectable emails, phone numbers, self-identified names, school affiliations, and addresses before transmitting free-form content. Filtering reduces exposure but cannot guarantee complete anonymization.
OpenAI’s API content is not used for model training by default unless the operator opts in. We have not opted in.

Before first use, you must acknowledge the AI Tutor processing notice, which describes these data handling practices.

AI Tutor Fair Use Policy: Paid All-Access includes up to 100 Tutor interactions per learner per day. The daily allowance resets on the learner’s local study day. Automated or shared-account use is prohibited under Section 10.

8. Educational Disclaimer

csmasters.dev is a supplementary educational resource. We do not issue official qualifications, credentials, certificates, or grades. Use of the Service does not guarantee any particular examination result. The Service is intended to complement, not replace, formal instruction.

9. Cambridge Non-Affiliation

csmasters.dev is NOT affiliated with, endorsed by, sponsored by, accredited by, or associated with Cambridge University Press & Assessment or Cambridge Assessment International Education (CAIE).

Cambridge, Cambridge IGCSE®, and Cambridge International AS & A Level® are registered trademarks of Cambridge University Press & Assessment. Any references to syllabus codes (e.g. 0478, 2210, 9618), examination specifications, or qualification names are made strictly under nominative fair use to describe the educational subject matter and curriculum alignment of our original exercises. All practice questions, autotests, code, and explanations are original creations of csmasters.dev.

10. Acceptable Use

You agree not to:

Reverse engineer, decompile, or extract source code from the Service (except as permitted by law)
Perform automated scraping outside of permitted robots.txt guidelines
Conduct denial-of-service attacks or exploit compiler execution endpoints
Share harmful, abusive, or inappropriate content with the AI Tutor
Share your account credentials or use multiple accounts
Use the Service for any illegal purpose

11. Suspension & Termination

We may suspend or terminate your account if you violate these Terms. Upon termination for cause, your access ends immediately. We will retain your data for a reasonable period to comply with legal obligations, after which it will be deleted. You may request account deletion at any time (see our Privacy Policy).

12. Intellectual Property

All curriculum content, exercises, explanations, platform design, and website assets are the exclusive intellectual property of csmasters.dev. Code written and submitted by users within exercises and the compiler workspace remains the intellectual property of the respective user.

13. Intellectual Property Inquiries & Takedown

We respect intellectual property rights. If you are a copyright or trademark owner (or authorized agent) and believe that content hosted on the Service infringes your rights, please submit a detailed notification to [email protected] including identification of the copyrighted work, the infringing material, and your contact information.

14. Limitation of Liability

The Service is provided “as is” and “as available” without warranties of any kind, express or implied. To the maximum extent permitted by applicable law, we shall not be liable for any indirect, incidental, special, consequential, or punitive damages arising from your use of or inability to use the Service.

15. Changes to These Terms

We may update these Terms from time to time. Each version is identified by its version date. Continued use of the Service after changes are posted constitutes acceptance of the updated Terms. We will notify registered users of material changes via email or a prominent notice on the Service.

16. Contact

For questions about these Terms, contact us at [email protected]. For legal inquiries, contact [email protected].