I am a big fan of Dr. Who and have always wanted to come up with a time travel mechanic and thought that time travel could be represented by the colours. Obviously the colours in the picture below are way to garish and would be muted or maybe just an outline of colour would be needed on each area. It might work if tertiary colours are added. Each line below represents a different time line – the primary colours could represent major events or places and the secondary colours steps along the continuum. By playing a combination of different coloured cards you can move back and forth along the time line – back and forward in time. When landing on one of the colours an event card/action or something takes place (remember this is just an idea right now). The secondary colours affect both primary colours – therefore affecting history and future events (tertiary colours could just affect future events or the primary colour they are closest to??). The only way you can jump onto another time line is by playing a primary colour and its complimentary colour. Feedback welcome.