system
Given the following post, respond as if you're commenting on Reddit:
human
If the speed of light is a constant independent of the speed of the observer - why does the doppler shift occur?

Is it that the light isn't slowed down or speed up, just that the wave itself becomes stretched or compacted yet propogates at the same speed?  
EDIT: Sorry I am not sure how to add the appropriate science tag - but I think it is a wonderful idea! Keep up the great work mods!
gpt
The Doppler shift occurs with light because regardless of the speed of light, it is still a wave.

Changing your reference frame causes you to perceive the 'peaks' and 'troughs' of the wave at a different rate.  Consider driving a boat over ocean waves.  If you drive towards or away from the direction of the waves, you can alter their perceived frequency.

This is true of any wave.