Notable features of Shivaji's forts include:
Design changes with the topography and in harmony of the contour, no monotony of design
No ornate palaces or dance floors or gardens
No temple complexes
Not much difference in the area of higher or lower ranks
Marvelous acoustics in the capital
Sanskritization of fort names
Community participation in the defense of forts
Three tier administration of forts
System of inspection of forts by higher ups including the king
Distinct feature of forts like double line fortification of Pratapgad, citadel of Rajgad
Foresight in selection of sites.
Source- wiki