added tutorial day 0

tutorial/day0/Day0.md

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+# Day 0 — Claude Code Setup
+
+This guide walks you through installing Claude Code on your machine and authenticating so you can start using it.
+
+## Step 1: Install Claude Code
+
+Choose your operating system:
+
+| OS | Guide |
+|----|-------|
+| Windows | [windows.md](windows.md) |
+| Linux | [linux.md](linux.md) |
+| macOS | [mac.md](mac.md) |
+
+Follow the guide for your OS, then come back here for authentication.
+
+---
+
+## Step 2: Verify Installation
+
+After following your OS-specific guide, confirm everything is working:
+
+```bash
+node --version    # Should show v18.x or higher
+claude --version  # Should show the installed Claude Code version
+```
+
+---
+
+## Step 3: Login
+
+<img src="assets/login.png" alt="Claude Code login screen" width="50%">
+
+Run `claude` in your terminal. On first launch, it will ask you to choose a login method.
+
+### Method 1: Subscription (Claude Pro / Max)
+
+- Select **Claude.ai account**
+- Browser opens — sign in and authorize
+- Return to terminal, you're logged in
+
+### Method 2: API Key (Pay-as-you-go)
+
+- Go to [console.anthropic.com](https://console.anthropic.com) → **API Keys** → **Create Key**
+- Select **Anthropic API Key** in the prompt
+- Paste your key (starts with `sk-ant-`)
+
+---

tutorial/day0/linux.md

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+# Linux Setup
+
+[Back to Day 0](Day0.md)
+
+## Prerequisites
+
+You need **Node.js v18 or higher** and **npm**.
+
+## Step 1: Install Node.js
+
+### Option A: Via nodejs.org Download Page with fnm (Recommended)
+
+**fnm** (Fast Node Manager) is officially recommended by Node.js. It's fast, lightweight, and lets you switch Node versions easily if needed later.
+
+1. Open your browser and go to [nodejs.org/en/download](https://nodejs.org/en/download).
+
+2. You'll see a row of dropdowns that says: **"Get Node.js® vXX.XX.X (LTS) for __ using __ with __"**. Set the dropdowns as follows:
+
+   | Dropdown | Select |
+   |----------|--------|
+   | Version | **vXX.XX.X (LTS)** — keep the default LTS version, don't change it |
+   | OS | **Linux** |
+   | Package Manager | **fnm** (under "Recommended (Official)") |
+   | Package Format | **npm** — keep the default |
+
+3. The page will show you the exact commands to run. Open your terminal and copy-paste them. They will look something like this:
+
+   ```bash
+   # Step 1 — Install fnm
+   curl -fsSL https://fnm.vercel.app/install | bash
+
+   # Step 2 — Restart your terminal or reload your shell profile
+   source ~/.bashrc   # or: source ~/.zshrc (if you use zsh)
+
+   # Step 3 — Install Node.js
+   fnm install 24   # The page will show the exact version number
+   ```
+
+   > The version number may differ from above — always use whatever the website shows.
+
+4. **Close and reopen your terminal** (or run the `source` command above) so that `fnm`, `node`, and `npm` are available.
+
+> **Why fnm?** It's in the "Recommended (Official)" category on the Node.js download page. Like nvm, it installs Node into your home directory so you never need `sudo` for npm global installs — but fnm is significantly faster (written in Rust) and works the same across Windows, macOS, and Linux.
+
+### Option B: Using your distro's package manager
+
+This is quicker but may install an older version of Node.js. **Check the version after installing** — if it's below v18, use Option A instead.
+
+**Ubuntu / Debian:**
+
+```bash
+sudo apt update
+sudo apt install -y nodejs npm
+
+# Check the version
+node --version   # Must be v18 or higher
+```
+
+**Fedora:**
+
+```bash
+sudo dnf install -y nodejs npm
+```
+
+**Arch Linux:**
+
+```bash
+sudo pacman -S nodejs npm
+```
+
+### Option C: NodeSource (Latest LTS via apt, no nvm)
+
+For Ubuntu/Debian users who want the latest LTS without using nvm:
+
+```bash
+curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
+sudo apt install -y nodejs
+```
+
+## Step 2: Verify Node.js
+
+```bash
+node --version
+npm --version
+```
+
+Both should print version numbers. `node --version` must show v18.x or higher.
+
+## Step 3: Install Claude Code
+
+```bash
+npm install -g @anthropic-ai/claude-code
+```
+
+> **Permission error?**
+> - If you used **fnm** or **nvm**: this shouldn't happen. Check that it's active (`which node` should point to a path inside your home directory, not `/usr/...`).
+> - If you used a system install: either use `sudo npm install -g @anthropic-ai/claude-code` or fix npm's global directory permissions:
+>   ```bash
+>   mkdir -p ~/.npm-global
+>   npm config set prefix '~/.npm-global'
+>   echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.bashrc
+>   source ~/.bashrc
+>   ```
+
+## Step 4: Verify Claude Code
+
+```bash
+claude --version
+```
+
+You should see the Claude Code version printed. Now head back to [Day0.md](Day0.md) for authentication setup.
+
+---
+
+## Notes
+
+- **WSL (Windows Subsystem for Linux):** This guide works inside WSL too. Just follow these steps from your WSL terminal.
+- **PATH issues:** If `claude` is not found after install, ensure npm's global bin is in your PATH. Run `npm config get prefix` — the `bin/` subdirectory of that path needs to be in your PATH.

tutorial/day0/mac.md

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+# macOS Setup
+
+[Back to Day 0](Day0.md)
+
+---
+
+**Terminal**
+- Open Terminal (press `Cmd + Space`, type "Terminal", hit Enter)
+
+**Homebrew**
+- Check if Homebrew is already installed:
+  ```bash
+  brew --version
+  ```
+- If you get "command not found", install Homebrew first:
+  ```bash
+  /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+  ```
+
+**Claude Code**
+- ```bash
+  brew install --cask claude-code
+  ```
+
+**Verify**
+- ```bash
+  claude --version
+  ```
+
+---
+
+Now head back to [Day0.md](Day0.md) for authentication setup.

tutorial/day0/windows.md

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+# Windows Setup
+
+[Back to Day 0](Day0.md)
+
+## Prerequisites
+
+You need **Node.js v18 or higher** and **npm** (bundled with Node.js).
+
+## Step 1: Install Node.js
+
+### Option A: Via nodejs.org Download Page with fnm (Recommended)
+
+**fnm** (Fast Node Manager) is officially recommended by Node.js. It's fast, lightweight, and lets you switch Node versions easily if needed later.
+
+1. Open your browser and go to [nodejs.org/en/download](https://nodejs.org/en/download).
+
+2. You'll see a row of dropdowns that says: **"Get Node.js® vXX.XX.X (LTS) for __ using __ with __"**. Set the dropdowns as follows:
+
+   | Dropdown | Select |
+   |----------|--------|
+   | Version | **vXX.XX.X (LTS)** — keep the default LTS version, don't change it |
+   | OS | **Windows** |
+   | Package Manager | **fnm** (under "Recommended (Official)") |
+   | Package Format | **npm** — keep the default |
+
+3. The page will show you the exact commands to run. Open **PowerShell as Administrator** (right-click the Start menu > "Terminal (Admin)" or search for PowerShell > right-click > "Run as administrator").
+
+4. Copy and paste the commands from the page. They will look something like this:
+
+   ```powershell
+   # Step 1 — Install fnm
+   winget install Schniz.fnm
+
+   # Step 2 — Configure fnm environment (add to your PowerShell profile)
+   fnm env --use-on-cd --shell powershell | Out-String | Invoke-Expression
+
+   # Step 3 — Install Node.js
+   fnm install 24   # The page will show the exact version number
+   ```
+
+   > The version number may differ from above — always use whatever the website shows.
+
+5. **Close and reopen your terminal** after installation. This is important so that `node` and `npm` are available in your PATH.
+
+> **Why fnm?** It's in the "Recommended (Official)" category on the Node.js download page, installs in seconds (written in Rust), and works natively on Windows — unlike nvm which requires a separate community port for Windows.
+
+### Option B: Official .msi Installer (Alternative)
+
+If you prefer a traditional installer:
+
+1. Go to [nodejs.org](https://nodejs.org). The homepage shows a big **"Download Node.js (LTS)"** button.
+2. Click it to download the `.msi` file.
+3. Run the installer:
+   - Click **Next** through the wizard.
+   - Accept the license agreement.
+   - Keep the default install location (`C:\Program Files\nodejs\`).
+   - On the "Tools for Native Modules" screen, **check the box** for "Automatically install the necessary tools" — this installs build tools you may need later.
+   - Click **Install** and wait for it to finish.
+4. **Restart your terminal** after installation.
+
+### Option C: Using winget (One-liner)
+
+If you have `winget` (built into Windows 10/11):
+
+```powershell
+winget install OpenJS.NodeJS.LTS
+```
+
+Close and reopen your terminal after installation.
+
+## Step 2: Verify Node.js
+
+Open a **new** terminal (Command Prompt, PowerShell, or Windows Terminal) and run:
+
+```powershell
+node --version
+npm --version
+```
+
+Both commands should print version numbers. If you get "not recognized", restart your terminal or check that Node.js is in your PATH.
+
+## Step 3: Install Claude Code
+
+```powershell
+npm install -g @anthropic-ai/claude-code
+```
+
+> If you get a permission error, open your terminal as **Administrator** (right-click > Run as administrator) and run the command again.
+
+## Step 4: Verify Claude Code
+
+```powershell
+claude --version
+```
+
+You should see the Claude Code version printed. Now head back to [Day0.md](Day0.md) for authentication setup.
+
+---
+
+## Notes
+
+- **Recommended terminal:** Windows Terminal or PowerShell. The classic Command Prompt works but has limited features.
+- **WSL users:** If you prefer running Claude Code inside WSL (Windows Subsystem for Linux), follow the [Linux guide](linux.md) instead — WSL is a full Linux environment.
+- **PATH issues:** If `claude` is not recognized after install, npm's global bin directory may not be in your PATH. Run `npm config get prefix` to find it, then add the resulting path to your system's PATH environment variable.