## 1. Project Setup

- [x] 1.1 Initialize Deno project with deno.json configuration
- [x] 1.2 Set up directory structure (src/, cli.ts)
- [x] 1.3 Add image processing dependency compatible with Deno

## 2. Core Image Scaling Implementation

- [x] 2.1 Create image loader module supporting PNG, JPEG, WebP, GIF
- [x] 2.2 Implement scale function with exact dimensions (stretch) mode
- [x] 2.3 Implement scale function with fit mode (preserve aspect ratio)
- [x] 2.4 Implement scale function with cover mode (preserve aspect ratio, crop)
- [x] 2.5 Create image saver module with format detection

## 3. Batch Processing

- [x] 3.1 Implement directory scanner for supported image formats
- [x] 3.2 Create batch processor with progress reporting
- [x] 3.3 Add error handling for failed images in batch

## 4. CLI Interface

- [x] 4.1 Create CLI argument parser (input, output, width, height, mode)
- [x] 4.2 Implement single image scaling command
- [x] 4.3 Implement batch scaling command (directory/multiple files)
- [x] 4.4 Add error messages and exit codes for invalid input
- [x] 4.5 Add help documentation (--help flag)

## 5. Testing & Validation

- [x] 5.1 Create test images for each supported format
- [x] 5.2 Write unit tests for scale functions
- [x] 5.3 Write integration tests for CLI commands
- [x] 5.4 Test batch processing with mixed formats
- [x] 5.5 Verify output dimensions match specifications