Lego Digital Designer lets you play with Legos - but these Legos are digital ones. Essentially, it's a 3D model editor that supports a wide range of Lego bricks.
To build a model in Lego Digital Designer, select the part you want to insert and place it in the work area. Use the arrow keys to rotate it. To remove a lego, select it and press the backspace key.
You can start a new model or modify an existing one, such as a tractor, a helicopter, an airplane, a tank, or a ship. You can even filter Lego blocks to find them more easily.