Might as well start making a milestone checklist.. 2 actually.. one tech, one content. And use K.I.S (Keep it simple)

Ex.:
Tech:
- Render fully textured room with reflections
- Fully textured room with shadow casting
- Room with bouncing ball (Physics)
- Positional Sound
- Sound reverb
- EAX Support

Content:
- Story
- Storyboard split in 'acts'
- Game script (story wise) per 'scene'

etc.