New school of thought or back to the drawing board?

• GLASS SKIN: Supporters say it has been tested as a non-reflective matt surface. Critics worry it will "overpower" the Mackintosh building, with sunlight bouncing off during the day.

• FACADE: The "monotonous facade" risks "vast, unrelieved areas of glass in the new building". These "risk neutralising the counterpoint of window and wall in the old one opposite," said critic William Curtis.

• LIGHT: Diagonal "driven void light shafts" meant to take light into the heart of the new building - but they risk becoming "dull holes" in grey winter days.

• GREENERY: Green garden area with a recycling water pond to be like "machair", the shoreline pasture found in the Outer Hebrides and on the north-west coast, thick with wildflowers in the spring.

• STUDIOS: Positioned at the top of the north faade (facing away from the Mackintosh building) with large windows to maximize access to the high-quality diffuse north light for artists.