diff --git a/.tool-versions b/.tool-versions
index 79900ee..1c42095 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,4 +1,4 @@
-nodejs 20.11.1
+nodejs 20.19.0
 ruby 3.3.3
 bundler 2.3.26
 cocoapods 1.15.2
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..d8e17c1
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,75 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+Oh My Zwift is a React Native/Expo mobile app that displays Zwift racing events and helps users predict race results. The app uses Expo Router for file-based navigation, NativeWind for styling, and TanStack Query for API state management.
+
+## Commands
+
+### Development
+
+```bash
+bun start              # Start Expo development server
+bun run ios           # Run on iOS simulator
+bun run android       # Run on Android emulator
+bun run web           # Run in web browser
+```
+
+### Testing
+
+```bash
+bun test              # Run tests in watch mode
+bun run test:ci       # Run tests once (CI mode)
+bun run test:coverage # Generate coverage report
+```
+
+### Code Quality
+
+```bash
+bun run lint          # Run ESLint
+bun run format        # Format code with Prettier
+bun run format:check  # Check formatting without fixing
+```
+
+## Architecture
+
+### File-based Routing
+
+The app uses Expo Router with the following structure:
+
+- `app/_layout.tsx` - Root layout with navigation setup
+- `app/index.tsx` - Home screen listing events
+- `app/events/[eventId]/index.tsx` - Dynamic event detail screens
+- `app/events/[eventId]/subgroups/[subgroupId]/index.tsx` - Subgroup details
+
+### API Integration
+
+- API calls are centralized in `api/` directory
+- Uses Axios for HTTP requests
+- TanStack Query for caching and state management
+- Base URL: https://zwift.taeho.io/api/v1
+
+### Styling System
+
+- NativeWind (Tailwind CSS for React Native)
+- Custom Zwift fonts (ZwiftSprint family)
+- Color system using CSS variables in `styles/global.css`
+- Utility function `cn()` for className merging in `styles/index.ts`
+
+### Type Definitions
+
+All API responses and domain models have TypeScript types in `types/`:
+
+- `zwift.type.ts` - Core Zwift types
+- `zwiftpower.type.ts` - ZwiftPower integration types
+- `zwiftracing.type.ts` - Racing-specific types
+- `supabase.database.type.ts` - Database schema types
+
+### Testing Approach
+
+- Jest with Expo preset
+- Test files in `__tests__` directories
+- Component testing with @testing-library/react-native
+- Snapshot testing for UI components
diff --git a/app/events/[eventId]/index.tsx b/app/events/[eventId]/index.tsx
index a3efde7..73ee60c 100644
--- a/app/events/[eventId]/index.tsx
+++ b/app/events/[eventId]/index.tsx
@@ -4,7 +4,6 @@ import { useCallback, useState } from "react";
 import {
   Dimensions,
   Image,
-  Platform,
   RefreshControl,
   SafeAreaView,
   ScrollView,
diff --git a/app/index.tsx b/app/index.tsx
index 25a5b3a..da0717c 100644
--- a/app/index.tsx
+++ b/app/index.tsx
@@ -54,7 +54,7 @@ export default function HomeScreen() {
         >
           <FadeInView>
             <EventList
-              className={cn("opacity-100 transition-all duration-500", {
+              className={cn("opacity-100 transition duration-500", {
                 "opacity-50": isRefreshing,
               })}
               eventsWithRoute={query.data}