Your First Session

Let’s do something real. In this lesson, you’ll use Claude Code to create a small project from scratch and experience the core interaction loop.

Start a Session

Create a fresh directory and launch Claude:

mkdir ~/ai-course-playground
cd ~/ai-course-playground
claude

Exercise 1: Create a File

Ask Claude to create a simple HTML file:

Create an index.html with a page that says "Hello from Claude Code"
with some basic styling

Watch what happens:

1. Claude will use its Write tool to create the file
2. You’ll see the file contents in your terminal
3. The file is immediately on your filesystem — open it in a browser

Exercise 2: Modify a File

Now ask Claude to change it:

Add a dark mode toggle button that switches between light and dark themes

Notice how Claude:

• Reads the existing file first
• Edits specific parts rather than rewriting everything
• Shows you the diff of what changed

Exercise 3: Ask Questions About Code

Explain how the dark mode toggle works

Claude can read and explain code it wrote or code you bring to it.

Exercise 4: Use the Shell

Create a package.json and install a local http server so I can preview this

Claude will:

• Use Bash to run npm init and npm install
• Suggest how to start the server
• You approve each command before it runs

The Interaction Loop

Every Claude Code session follows this pattern:

1. You describe what you want (natural language)
2. Claude plans an approach (sometimes visible, sometimes implicit)
3. Claude takes actions (read, write, edit, run commands)
4. You review and approve (or deny and redirect)
5. Repeat

The key insight: you’re not writing code and asking Claude to review it. You’re describing intent and Claude is doing the implementation. Your job shifts from writing to directing and reviewing.

Tips for Effective Sessions

• Be specific about what you want, vague about how to do it
• Let Claude read existing code before asking it to modify things
• Review diffs carefully — Claude is good but not perfect
• Use follow-up messages to refine — “make the button bigger”, “use a different color”
• Don’t restart sessions unnecessarily — Claude remembers the full conversation

Clean Up

You can keep the playground directory for experimentation throughout the course, or remove it:

rm -rf ~/ai-course-playground

You’ve now completed your first real Claude Code session. Next, we’ll dive deep into the fundamentals.