Design a portable restroom with the following features: 1. **Color**: Change from blue to a vibrant green. 2. **Shape**: Keep the rectangular design but add a slightly curved roof for a modern look. 3. **Interior Layout**: Include a small shelf above the toilet for personal items, and replace the existing black pipe with a discreet ventilation grate. 4. **Entrance**: Create a single, wider door that swings outwards and has a locking mechanism. 5. **Signage**: Use simple, unmarked symbols for gender identification instead of any brand references. This design should maintain functionality while incorporating fresh, appealing elements.