Next.js Master Class: Part 1 Learning the Essence of App Router and Rendering Design through Missions

We solve the fundamental problem of losing control amidst AI-generated fragmented code and the complex React ecosystem by opening the hood and engineeringly analyzing the internal workings of core React libraries such as Zustand, TanStack Query, React Hook Form, Zod, and the React Compiler. By moving beyond simple tool usage and mastering how to directly manipulate the performance and data flow of the React engine, you will build the solid 'enterprise architecture design muscle' necessary to respond immediately to any crisis.

This is not just a lecture you listen to and forget. This course aims not for "the moment you understand React," but for "the moment you can actually work with React." In every section, you'll complete missions alongside the lectures, solve practice problems yourself, and learn by implementing core concepts like JSX, Virtual DOM, State, and useEffect with your own hands. When you finish the course, you won't just be a beginner who knows React syntax—you'll be a developer who can explain and utilize everything from component design to rendering flow on your own. "Not a class you just listen to, but learning you build through completion." Understand the essence of React and experience the world of declarative UI firsthand.

The real world is unforgiving. I will thoroughly pass on my optimization expertise through a meticulous mission system, showing you how to design smooth user experiences even in extreme environments where tens of thousands of real-time data points pour in. Go beyond simply writing code and leap forward to become an irreplaceable senior engineer who dissects performance through understanding engine principles.

An Express.js journey from beginner to mastery, flowing like water! A backend journey where you learn properly by directly implementing from basic server concepts to completing a CRUD project.

This course goes beyond just using Express.js—you'll implement its internal engine from scratch to truly understand how real servers work. You'll gain hands-on experience growing as a server developer by building all of Express's components from the ground up, including routers, middleware, request-response objects, static file handling, and template rendering.

This course is a full-stack level frontend project course that focuses on implementing Notion from start to finish using Vanilla JavaScript, going beyond simple UI cloning to deeply understand the internal operating principles. You'll implement all the core features of a real note-taking app using vanilla JS, including sidebar tree, nested document creation, auto-save, routing, trash, favorites, search modal, settings modal, theme switching, Export/Import, keyboard shortcuts, responsive layout, drag resize, and more. The goal is to solidly learn browser standard behaviors (event bubbling, DOM tree, local storage, Blob, FileReader, hash routing, etc.) that you must know before frameworks like React and Vue, so you can completely understand "why it works this way" and build the skills to debug effectively.

No matter how much you study React, Next.js, or Vue, if the code feels abstract and the structure isn't clearly understood, the root cause might be a lack of understanding of DOM. DOM is the foundation of all frontend frameworks and the entity that connects the structure and behavior of web pages. This lecture goes beyond simple selectors or manipulation methods, teaching step-by-step from the very beginning how HTML transforms into DOM objects and how to select, traverse, and manipulate this structure. It is the Part 1 introductory lecture of 'Complete DOM Mastery'. HTML tags are just structure, and JavaScript is just behavior, but DOM is the core that connects the two. If you clearly understand this connection, you'll be able to precisely grasp the true structure and flow within any framework you use.

Have you ever thought about building a 'real system' beyond simply rendering screens? The real problem many developers commonly face is something else entirely. It's the limitation of a 'fake full-stack'—where things look plausible on the surface, but data synchronization frequently tangles, speed is frustrating, and you lose track of where to even start when just a few features are added. This isn't a problem that can be solved by simply memorizing one more Next.js feature. This course will resolve that frustration from the roots. Encyclopedia-style classes that just list features are boring, aren't they? Instead, we have tightly integrated the fundamental principles of Computer Science (CS) with the advanced architecture of Next.js. We will directly transplant into your fingertips the enterprise-level design skills required to flexibly withstand millions of visitors and maintain perfect data consistency.

This course covers the entire Critical Rendering Path (CRP) process, from the moment the browser receives HTML to create the DOM, to combining it with the CSSOM and painting pixels on the screen. Moving beyond simple DOM manipulation, you will learn how CSS and JS impact performance, as well as practical strategies to noticeably improve real-world web performance—including image and font optimization, Lazy Loading, Intersection Observer, virtual lists, and hands-on practice with DevTools.

This course goes beyond simply using Express.js. You will rebuild its internal engine from start to finish, gaining hands-on experience with the real principles of how a server works. By directly creating each component of Express—such as routing, middleware, request–response objects, static file handling, and template rendering—you will grow as a server developer and truly understand how a framework operates at its core.

This course goes beyond simple DOM manipulation, deeply learning how to dynamically compose and react to web UIs within interactions with actual users. It's structured for you to learn by directly implementing common issues encountered in practice, from the essence of event systems, bubbling and capturing, event delegation, real-time UX feedback, to performance optimization using throttle & debounce. Based on an understanding of the DOM tree structure, you will develop the ability to flexibly connect event flow and state changes.

📌 This course is a curriculum that starts with a strategic AI tic-tac-toe project and completes core object-oriented programming concepts through practical examples. You'll train logic design and AI strategic thinking through game implementation, then directly experience OOP design techniques like inheritance, composition, delegation, and encapsulation through code. This is recommended for those who want to grow beyond syntax into a 'developer who designs' through real projects.

Through this course, students will broadly learn the basics and advanced concepts of JavaScript, from setting up the development environment to variables, conditional statements, functions, objects, and arrays. Through thorough review with practice exercises and quizzes, they will be able to develop problem-solving skills that can be immediately applied to web and mobile development practices.

This course systematically masters intermediate to advanced CSS techniques such as "CSS Position, Transition, Transform, Animation, Flexbox, Grid, and Responsive Web Design," and equips you with skills immediately applicable in real-world projects through various hands-on practice projects.

The "Learning HTML + CSS Properly: Complete Mastery from Beginner to Practical Application Part 1" course is designed to provide a deep understanding of how the internet and the web work, and to solidify the basics of HTML/CSS through a practice-oriented curriculum. By taking this course, you can firmly grasp the essential concepts of web development and immediately apply them to projects.

This is not just a lecture you listen to and forget. This course aims not for "the moment you understand React," but for "the moment you can actually work with React." In every section, you'll complete missions alongside the lectures, solve practice problems yourself, and learn by implementing core concepts like JSX, Virtual DOM, State, and useEffect with your own hands. When you finish the course, you won't just be a beginner who knows React syntax—you'll be a developer who can explain and utilize everything from component design to rendering flow on your own. "Not a class you just listen to, but learning you build through completion." Understand the essence of React and experience the world of declarative UI firsthand.

The real world is unforgiving. I will thoroughly pass on my optimization expertise through a meticulous mission system, showing you how to design smooth user experiences even in extreme environments where tens of thousands of real-time data points pour in. Go beyond simply writing code and leap forward to become an irreplaceable senior engineer who dissects performance through understanding engine principles.

We solve the fundamental problem of losing control amidst AI-generated fragmented code and the complex React ecosystem by opening the hood and engineeringly analyzing the internal workings of core React libraries such as Zustand, TanStack Query, React Hook Form, Zod, and the React Compiler. By moving beyond simple tool usage and mastering how to directly manipulate the performance and data flow of the React engine, you will build the solid 'enterprise architecture design muscle' necessary to respond immediately to any crisis.

Let's delve into the source code together, from technical interviews to practical design. I'll help you develop the deep understanding and unique perspective necessary for the AI era. Grow from a developer who simply "used" Next.js to an expert who "understands" why it's used that way.

Learn Springboot + NextJS RestAPI Board Creation Faster Than Anyone! Develop a CRUD server with Springboot and create your own board with NextJS!

This course starts with the question "If I had been on the Titanic, could I have survived?" and completes a full-stack project that develops an AI model to predict survival probability based on actual data and serves it as a web service. You'll practice the entire process of AI and web development, from deep learning modeling using PyTorch, building a backend server with FastAPI, to implementing a user interface with Next.js.

Firebase's SQL version! You can master the basics of Next.js full-stack development through Supabase!

A lecture that allows you to clearly understand the basic concepts of React by learning with illustrations.

This course will help you develop mobile apps that can be serviced on Android and iOS using web development.

This is the most solid foundation course for beginners who want to learn JavaScript properly. This course will be the starting point for understanding the language called JavaScript, and you can perfectly prepare the basics to become a front-end (Vue, React, Angular) developer and server (Node.js) developer.

Developing an AI Safety Report Service with React + Spring AI The 5th Neo + Essential project lecture is about building a Safety Report system, an idea for improving government systems!

This course goes beyond just using Express.js—you'll implement its internal engine from scratch to truly understand how real servers work. You'll gain hands-on experience growing as a server developer by building all of Express's components from the ground up, including routers, middleware, request-response objects, static file handling, and template rendering.

This is a practical course where you will directly create a timer app using React, Electron, and Zustand, and even deploy it to cross-platforms (Windows, macOS, Linux). Starting with familiar React web development, you can learn the entire flow of desktop app development, including global state management via Zustand and final GUI deployment!

In the era of swift execution and validation, execute faster than anyone with VIBE Coding! Achieve complete monetization, from ads to payments, all by yourself.

Based on the experience of wondering how facial recognition works in offline environments on-site, this course will guide you through building the basic structure of a facial recognition-based access and attendance management system using React + Electron and Python's FastAPI-based DeepFace. Rather than focusing on perfection, we focus on understanding the operating principles and laying the foundation for you to expand into your own personal projects.

This course goes beyond simply using Express.js. You will rebuild its internal engine from start to finish, gaining hands-on experience with the real principles of how a server works. By directly creating each component of Express—such as routing, middleware, request–response objects, static file handling, and template rendering—you will grow as a server developer and truly understand how a framework operates at its core.

In this course, you will learn about TypeScript.

Building your own emotional diary service with Spring AI + React It's time for our 4th project with Neo + Essential!

AI is no longer a choice, but a matter of survival. Shorten development tasks that used to take 3 days down to 30 minutes; leave repetitive tasks to AI and focus on solving more important problems. Through AI-native development methods that are practical rather than theoretical, we will show you the definitive way to be recognized as an "AI-savvy developer" at your company.

You will learn the process of developing and launching your own restaurant diary app using React Native. We've prepared the entire process from design to front-end and back-end development, and deployment.