The ornamental design for a platformsystem, as shown and described.
FIG. 1 is a perspective view of a platform system showing my new design;
FIG. 2 is a front elevation view of the platform system of FIG. 1;
FIG. 3 is a rear elevation view of the platform system of FIG. 1;
FIG. 4 is a right side elevation view of the platform system of FIG. 1;
FIG. 5 is a left side elevation view of the platform system of FIG. 1;
FIG. 6 is a top plan view of the platform system of FIG. 1; and,
FIG. 7 is a bottom plan view of the platform system of FIG. 1.
The broken lines showing the tread pattern and hand rail kick plate in the figures are included for the purpose of illustrating portions of the platform system which form no part of the claimed design.