Lightweight, privacy-first apps that work offline and need no account: generate a legal complaint in 3 minutes, hit your protein goal, never lose a discount QR. Everything stays on your phone — open in the browser or install in seconds.
Four focused tools, live now and free to start — plus the All-Access bundle for the whole portfolio of 19 apps. One-time Pro, no subscriptions.
Your daily nutrition assistant
Hit your daily protein goal with quick-add meals, water tracking and honest weekly stats.
Never miss a discount again
Scan discount QR codes from the shelf or your camera and keep them organized with store, notes and expiry dates.
AI-generated complaints with legal citations
Describe the problem, get a professional complaint — correctly cited to CZ/SK/EU law, ready to send.
Every app below works offline, needs no account, and is part of the Casuyi All-Access bundle.
All 20 apps. One purchase. No subscription.
One-time purchase · works offline · Czech, Slovak, German, English
Includes the current Casuyi app portfolio. Individual apps can also be purchased separately.
Guides that solve a specific problem — and tools that crunch the result for you.
A letter generator you can send in 3 minutes.
When you are entitled to it — a §-based decider.
30-day deadline calculator and what to do after it.
Steps, deadlines and a complaint generator with e-mail.
Generate a contract withdrawal form for free.
How much you save with an extra payment — annuity or equal.
Daily g target by weight, age and activity.
Checklist + a graveyard to track them.
Generator of a cancellation notice with proof of delivery.
8 red flags + a verdict calculator for staged sales.
Storage days, fees, and what happens after.
How long it lasts, what is excluded — expiry calculator.
When to report, how to read — consumption calculator.
What to photograph before damage happens — free app.
STK, emissions, smoke detectors — deadline calculator.
An expiry tracker so coupons never die in your gallery.
What actually lands on your account — 2026 levies included.
1RM estimator + weekly volume checker.
30-day grid and the 80 % rule, not perfectionism.
BMI, waist-to-height and water target in one go.
Vaccine and deworming dates your vet will ask about.
Intervals per plant + next-watering schedule.
SMART plan generator with 4 milestones.
Inspection checklist + what a 60-second OBD scan catches.
Blinking or steady: a decide-what-to-do guide.
What incomplete monitors mean and how to fix them.
P0420, P0300 and friends — meaning and severity free.
What Premium really costs — 3-year calculator.
Deals, platforms and the effective monthly rate.
How protein goals are counted — free calculator.
What your paid apps cost per year — savings check.
12-month instalment calendar with interest — free, printable.
Compare both payoff strategies on your real numbers.
Every bill in one month grid — heaviest week included.
How many months to your goal — or the monthly amount needed.
12-month repayment plan with interest — printable, free.
Two payoff strategies, compared on your numbers.
Every household due date in one month grid.
Months to your goal — or the monthly amount needed.
Built different — with your privacy and experience in mind.
All your data stays on your device. No accounts, no tracking, no cloud — your information is yours alone.
Optimized Progressive Web Apps that load instantly and work smoothly even on older devices.
No internet? No problem. All apps function perfectly without connectivity — perfect for anywhere, anytime.
Available in Czech, Slovak, and English. Built for the local market with international quality.
Free to start, premium features available via one-time purchase — no subscriptions, no surprises.
Regular improvements and new features based on user feedback. We listen and deliver.
Every app is live now — free to start, no account, installable on your phone. Questions, ideas or problems? We read everything.
Transparency and trust — our legal documents.
Last updated: August 20, 2026
Casuyi is committed to protecting your privacy. This Privacy Policy explains how we handle data in our mobile applications.
All information you enter into our applications (products, payments, packages, complaint drafts, etc.) is stored exclusively on your device using local IndexedDB storage. Nothing leaves your device.
• No accounts are required
• No cloud synchronization
• No analytics or tracking
• No third-party data sharing
When you purchase a Premium / Pro license via Stripe Payment Links:
• Payment information is handled entirely by Stripe (stripe.com)
• We do NOT store your credit card or payment details
• We store only your e-mail address from the checkout
• Your e-mail is used solely to verify your purchase and issue/activate your Pro license — it is never used for marketing, never sold, and never shared with third parties
Processing of your e-mail address is necessary to perform our agreement with you (Art. 6(1)(b) GDPR): we need it to deliver the license you purchased. No separate consent is required for this purpose.
Our applications do not use cookies. This landing page does not set any cookies or load third-party tracker scripts (analytics is currently disabled).
Our apps are designed with privacy-by-design principles and comply with:
• EU General Data Protection Regulation (GDPR)
• Czech Act No. 110/2019 Coll., on personal data protection
• EU ePrivacy Directive
Our applications are designed for all ages and do not collect data from children. Parental guidance is recommended for users under 16 years of age.
You have the right to:
• Access — request a copy of the personal data we hold about you (in practice: the e-mail address from your purchase)
• Erasure — request deletion of your e-mail address and purchase record (this deactivates the associated Pro license)
• Rectification — correct your e-mail address if it has changed
To exercise any of these rights, e-mail us from or including the address you used at checkout.
If you have questions about this Privacy Policy, contact us at:
Casuyi
appvantagelabs2@gmail.com
Last updated: August 17, 2026
By downloading, installing, or using any application published by Casuyi (collectively, the "Apps"), you agree to these Terms of Service ("Terms"). If you do not agree to these Terms, do not use the Apps.
Casuyi provides mobile web applications (Progressive Web Apps) for personal use. The Apps are designed to work offline on your device and do not require internet connectivity for core functionality.
Each App includes free features available at no charge. Premium features are available via one-time payment through Stripe Payment Links. The Premium purchase:
• Is a one-time payment — not a recurring subscription
• Grants lifetime access to Premium features
• Is non-refundable once the Premium unlock code has been applied to your account
• Applies only to your device and cannot be transferred
All Apps are licensed under the MIT License (see below). The MIT License allows you to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the software. However, the brand name "Casuyi" and the app icons/graphics may not be used without express permission.
THE APPS ARE 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 ARISING FROM, OUT OF OR IN CONNECTION WITH THE APPS.
In no event shall Casuyi be liable for any indirect, incidental, special, consequential, or punitive damages, including without limitation, loss of profits, data, use, goodwill, or other intangible losses, resulting from your access to or use of (or inability to access or use) the Apps.
We reserve the right to modify these Terms at any time. We will notify users of material changes via our website. Your continued use of the Apps after such modifications constitutes your acceptance of the updated Terms.
These Terms shall be governed by and construed in accordance with the laws of the Czech Republic. Any disputes arising from these Terms shall be resolved in the courts of the Czech Republic.
Copyright (c) 2026 Casuyi
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.
In accordance with the Czech E-Commerce Act (Act No. 36/2000 Coll.) and applicable EU digital services regulations:
Operator:
Casuyi — sole proprietorship (freelance)
Czech Republic
Business Registration:
Not operated as a registered company. No company registration number (IČO) or taxpayer ID (DIČ) — services are provided by a private individual as a sole proprietor.
Contact:
Email: appvantagelabs2@gmail.com
Website: casuyi.com
Dispute Resolution:
The European Commission provides an online platform for dispute resolution (ODR platform): https://ec.europa.eu/consumers/odr
We are not willing or obliged to participate in dispute resolution proceedings before a consumer arbitration board.