MLCAD
MLCAD (Mike's LEGO Computer Aided Design) is a virtual modeling program designed for use with LEGO parts. Using the LDraw LEGO parts library, it provides the ability to build almost any LEGO model virtually with an unlimited amount of bricks. The program is for people who enjoy building with LEGO bricks, but cannot store or afford as many bricks as they need to complete their structure.
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