Vastu Shastra is an ancient science energy flow throughout the house/office/factory that allows inflow of fresh air and natural light that promotes health, wealth, peace and happiness.

The most ancient science of architecture that goes back to the Vedic ages, it is composed of specific rules and regulations, set down by sages of those times, that an architect / builder / owner was expected to religiously follow to avoid coming under negative or evil influences. Today, it is looked upon as a highly evolved, comprehensive building philosophy in which directions and shapes are the most vital aspects of designing.

Right from the selection of site to correct slope of land down to the shape of the building, this oldest form of architecture covers nearly every aspect of construction. Not only for houses but temples, palaces, forts, offices...just about every possible form of construction. Often providing relief if not cures to physical or emotional problems simply by relocating an entrance, window or room.

Some of the important points made therein are :

Directional Alignment || Shape Of The Site || Slope Of The Land Surface|| Impact of Gates At Various Locations || Brahmasthan (Central Zone of the Building) || The Staircase || Inner Planning of a House || Inner Planning of an Office || Internal Planning of any Industrial Building

Directional Alignment

The directional axis of the plot should be properly aligned with the axis of the earth's magnetic field.
Boundaries AC & BD should be parallel to a north-south axis. While boundaries AB & CD should be in an East-West alignment.
Otherwise, such land will remain averse to overall growth, peace & happiness of those that shall inhabit it.

Figure (a) shows directional alignment

Figure (b) shows a non directionally aligned plot.

The geometrical axis of the plot should be properly aligned with the axis of the earth's magnetic field. i.e. one set of boundaries should be parallel to the north south axis and the other to the east -west axis as shown in the figure (a) and (b). 

Shape Of The Site
Symmetrical shapes like square or rectangular, circular & hexagonal promote overall growth, increases mental capabilities and generates prosperity.
Asymmetrical shapes like oval, triangular, parallelogram, star & trident are deemed inauspicious.