Hello, I am an individual developer with over 4 years of experience, working officially through a sole proprietorship. My specialization is system development in C++, so I will personally create the application architecture: I will set up an AES cryptographic module compatible with older operating systems, integrate SQLite for progress tracking, and implement an interface in Qt that will work instantly even on weak hardware, ensuring direct communication and transparency in development. My portfolio: 3magency.co, https://vilors.studio/.

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Welcome, we are a small team that has been creating complex digital products and offline platforms turn-key for over 4 years. We offer a comprehensive approach to developing your application: from designing the relational data structure in SQLite to integrating media engines and packaging distributions for each target OS (Inno Setup for Windows and .deb/.AppImage for Ubuntu), ensuring stable operation of quizzes and lessons without internet access. Our results: freshagro.com.ua, farfieworldwide.com, rivnekolo.com.

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Good day, my colleague and I have been specializing in the development of secure desktop software and system automation in C++/Qt for over 4 years. We will ensure strict compliance with security requirements: we will set up streaming decryption of media files in memory through a custom QIODevice, optimize SQLite queries for saving progress, and develop stable build configurations in Visual Studio 2019 with support for Windows XP and Ubuntu 22.04 targets. Please check our technical cases: drkukharevich.rivne.ua, crave-agency.com.ua, jk-solution.com.ua.

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Hello, my partner (designer + C++/Qt developer) and I are ready to implement your educational application, having over 4 years of joint experience. I will take care of the cross-platform architecture on Qt, implementing secure playback of encrypted video via AES + FFmpeg without saving to disk and using SQLite database, while my partner will develop a lightweight, adaptive, and modern UI/UX in the style of Duolingo based on QWidgets or lightweight QML, which will not burden outdated systems. Our joint works: hyperfi.tech, espressolab.com.ua, hudi.com.ua.

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❤️Hi, hope you are doing well.

I am a senior fullstack engineer with extensive experiences in C++, Qt 5.10/5.15, Visual Studio 2019, SQLite, multimedia playback, encryption/decryption, Windows/Linux desktop development, and offline-first application architecture.

This application needs a stable offline architecture that works across both legacy Windows versions and Ubuntu without losing performance or security. I can build the Qt/C++ desktop app with interactive lessons, quizzes, local progress tracking, SQLite storage, and a clean Duolingo-style UI adapted for desktop use.

For the encrypted video system, I can implement secure local media storage, controlled decryption during playback, and protection against direct file access using a lightweight approach compatible with older Windows environments. I can also handle packaging and testing for Windows XP/7/10/11 and Ubuntu 22.04.

Best Regards.
… Youssef

Dear Client,

I am very interested in your project. I can develop a fully offline educational desktop application (Duolingo-style) using C++ and Qt 5.15.
My Relevant Experience:
Over 7 years of commercial C++ / Qt desktop development
Extensive experience with Qt 5.10 – Qt 5.15
Strong background in cross-platform development (Windows + Linux)
Windows XP / Windows 7 compatibility — I have successfully delivered several projects that run on legacy Windows systems
Experience with SQLite, video playback (Qt Multimedia + FFmpeg), and secure local content (video encryption/decryption)
… Offline-first architecture, user progress tracking, interactive lessons and quizzes

Key Technical Approach:
Framework: Qt 5.15 (LTS) — as requested
Compiler: MSVC 2019 (Visual Studio 2019)
Windows XP/7 support: Static linking + careful dependency management
Video Encryption: AES-256 (or lighter AES-128 for XP compatibility) + secure decryption on-the-fly
Database: SQLite with encryption (SQLCipher)
Linux: Full support for Ubuntu 22.04
Packaging: Professional installers (Inno Setup for Windows, AppImage/DEB for Linux)

I can deliver a lightweight, secure, and modern application with excellent performance even on older hardware.
Project Conditions:
Timeline: 8–12 weeks (MVP in 5–6 weeks)
Full source code + detailed documentation
Testing on all required platforms (XP, 7, 10, 11 + Ubuntu 22.04)

I am ready to sign an NDA and start with a detailed technical discussion.
Next Step: Please send me more details about the project (especially the volume of content, desired UI style, and exact requirements for video encryption). I can also provide examples of my previous Qt desktop applications.
Looking forward to working with you on this interesting educational project.
Best regards,

Hello! After reviewing your project, I am ready to start working on it. I can offer optimal solutions to achieve the best results.

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Welcome! We are a team with 4 years of experience in system software development and UI/UX design. We are happy to implement your project and create a fast and stable desktop application based on C++ and the Qt framework.
We combine a deep understanding of low-level programming and code optimization with expertise in interface ergonomics. This allows us to create applications that not only withstand high loads but also have an intuitive GUI.

We write documented code that is easy to maintain and provide support during the application release stage.
We are ready to review your specifications or prototypes to discuss the architecture!

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Hi there!

An offline Duolingo style desktop app with secure local video is very doable in Qt and C++, and the tricky part is making it feel modern while still behaving nicely on Windows XP and Windows 7. I can build this in Qt 5.10 or 5.15 with Visual Studio 2019, keep the codebase portable for Ubuntu 22.04, and make sure the app stays lightweight with clean memory use and fast startup.

For the lesson and quiz engine, I would structure it as small reusable screens with a simple state machine so you can add new lesson types without rewriting the whole UI. SQLite will store users, progress, lesson results, and local content indexes, and I can make it resilient with migrations so updates do not break existing installs.

For the encrypted video system, I would use a practical approach that works on older Windows: encrypt the video files on disk and decrypt only short chunks in memory during playback, never writing decrypted files back to disk. This keeps file access protection reasonable while staying fast enough for smooth playback. If you prefer, we can run playback through a custom QIODevice that feeds decrypted bytes to the player, so the UI never touches raw media files.

One feature idea is an Offline Content Vault screen that shows what is installed, what is locked, and what is ready to learn, with a one click repair check that validates hashes and reindexes the SQLite catalog if anything looks corrupted. It reduces support headaches and builds user trust because everything stays self contained.
…
Budget and timeline estimate: $2,000 to $3,000 depending on how many lesson types and quiz modes you need in v1 and how strict the video protection layer must be, with an initial usable build in 10 days and a polished cross platform release in 3 to 4 weeks.

Thank you!

Hello! I am highly interested in your educational desktop application project. I have extensive experience with C++/Qt development and implementing secure data systems (encryption, API integration, and system emulation).

I can fully implement the required functionality according to your specifications:

Legacy Support: I will ensure stable performance on Windows XP and 7 using the appropriate toolsets in Visual Studio 2019 (v141_xp) and Qt 5.10/5.15.

Security & Encryption: I will build a secure local SQLite database and a protected video playback system. I’ll use AES encryption for "on-the-fly" decryption to prevent direct media file access.

UI/UX: I will create a modern, lightweight Duolingo-style interface, optimized for both legacy and modern systems.
…
Cross-platform: I will ensure seamless performance across both Windows and Ubuntu 22.04 environments.

I am well-versed in performance optimization and memory management. I am ready to discuss the project architecture and start immediately.

Good afternoon. If C++ is not essential, I can create such an application in Python + PyQt6. I have already worked with FFmpeg and SQLite. You can view examples of my work in the portfolio.

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Hello! I am ready to help with your project. I have extensive experience in development and can implement all the necessary components according to your documentation. I guarantee quality execution within the agreed deadlines.

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