The recently launched Audi TT is notable for its interior design, especially the unique design of the air-conditioning controls that are integrated into the air-vents:

HVAC (Heating, Ventilation, Air-Conditioning) controls on the 2015 Audi TT  

This is an excellent design. 

Fundamentally, changing something like the A/C temperature or fan speed involves two senses. Sight is needed to observe what the currently displayed temperature is and to then adjust the setting. Secondly, touch, or more specifically, thermoception, is needed to 'feel' the new temperature or fan speed change and confirm whether the new setting is appropriate, or whether further adjustment is required.

Thus, this process usually involves a two-step action: manipulating the switch or dial to change the temperature/air-flow, and then placing a hand near the air vent to 'feel' whether the new temperature and air-flow is right.

Most car interiors reinforce this two step process by separating the air-vent and temperature controls and placing them in disparate locations.

2017 Porsche 718 Boxster. The HVAC controls are just visible at the bottom of the image.

An example of this is the Porsche 718 Boxster. Porsche takes a contrasting approach to Audi and places its HVAC controls almost diametrically opposite to the air-vents, with both being separated by the infotainment screen and the media controls. Consequently, this design enforces the rigid two-step process outlined above, by forcing the driver to physically move their hand between two different locations in order to ensure the correct temperature and airflow setting.

Audi's design, in contrast, is innovative because it elegantly and efficiently combines the disparate two step process in the Porsche and other vehicles. By integrating all necessary HVAC controls, including temperature, fan speed and airflow within the air-vent, the driver can simultaneously adjust the control and immediately feel the effect of their action, without having to physically move their arm.

While this may seem to be a superficial change, Audi's design has numerous benefits. Not only does it create a sense of harmony and visual symmetry, but by minimising the number of separate buttons and switches, it greatly reduces the potential for the driver to be confused or frustrated by excessive clutter and small, illogically placed controls. By streamlining a relatively complicated, two-step process into a single action, Audi's design could also potentially increase road safety, by essentially halving the time the driver spends with one hand on the steering wheel.

An innovative, refreshing and logical design that clearly moves the ball forward. Great work.