Seven lightweight, privacy-first apps that work offline and need no account: track your nutrition, never miss a payment, see through fake sales, and more. Everything stays on your phone — open in the browser or install in seconds.
Seven lightweight, privacy-first tools — live now, free to start, with a one-time Pro upgrade on every app.
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.
Never miss a payment again
All bills and due dates in one place — see the category breakdown, stay ahead of deadlines.
See through fake sales
Track real prices over time so you know whether the “sale” is a sale — or marketing.
Know when someone picks up your package
Track packages at pickup points with a full timeline of every stop across all your orders.
AI-generated complaints with legal citations
Describe the problem, get a professional complaint — correctly cited to CZ/SK/EU law, ready to send.
Stop overpaying for forgotten subs
Every subscription in one place — see the full cost picture, cancel what you don't need, keep what you love.
Read your meters, see the real cost of energy
Electricity, gas, water, heat — monthly readings, automatic consumption × price, 12-month trends and year-over-year comparison.
Your home inventory — ready for the insurer
Categorize every item in the house with values and photos. After a flood, break-in or fire, hand your insurer a finished claim list in five minutes.
Gross to net in a second — Czech rates 2025 & 2026
See your exact net salary: progressive 15/23% tax, social and health insurance with statutory limits, tax relief for children, 13th salary and the tax bonus. Pro adds sick pay, employer cost and a month-by-month table.
Platební plán půjčky — víš, kolik ušetříš
Spočítej si, kolik ti půjčka doopravdy stojí: splátky, celkový úrok a amortizační tabulka — anuita i rovná. Pro přidává simulace předčasných splátek, srovnání úvěrů na refinanci a test úrokové sazby.
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.