Maxis shared a massive amount of details in their recent The Sims 4 livestream. They mostly got into the details of Build Mode, but also shared some insight into Live Mode and Gallery. Unless otherwise stated, the details here come from Build Mode.
There are five to eight rooms available for each room category. Room categories include the bedroom, bathroom, living room, and kitchen. Maxis demonstrated a styled room with three preset color schemes.
You can unlock styled rooms as career rewards. For example, artists can unlock studios, and chefs can unlock chef’s kitchens. These career themed rooms have career specific objects in them.
There were also three presets for wall height. Each wall height has a corresponding door height. Maxis did not make it clear if you can manually adjust these heights.
Kids rooms have five styles, and three preset color schemes for each room.
The design tool allows you to click an object to open up a menu of preset colors. They demonstrated this on a bed, which had half a dozen preset color combinations.
After the Maxis devs built four rooms, they added the foundation. There is an adjustable foundation height slider, which forces the rest of the house to adjust automatically. So, you can intuitively make a house roomier or tighter.
You can apply different cosmetic styles to each room, and you can also purchase items meant for other styled rooms and place them in a room you are building.
There are auto windows, auto stairs, and auto roof tools to fill out a house automatically, making house building that much easier. You can drag stairs to make them wider and thinner, and click once to space windows evenly. Windows can also be placed at different heights. In fact, anything you put on the walls can be height adjusted. The roof eaves can be adjusted together, or you can hold shift to adjust each side separately.
You can make a floating room, with no cantilevers or support. Maxis even explains that you can make a room float higher by copying it on top of itself, and then deleting the rooms below.
In Live Mode, the devs demonstrated an entertainment object called a Motion Gaming Rig. A Sim got to play a Tetris like game, but was able to use his hands to move the virtual blocks into rows and columns inside the well.
In Gallery, you can share an entire house, or you can pick out individual rooms to display. Anything you upload to the gallery gets saved locally in your PC.
Finally, Maxis demonstrated a resize cheat, that made a small fruit bowl on a counter top bigger than the house it was in.
The Sims 4 will be released on Windows on September 2, and on a still unannounced date on Mac.