The interface is primarily mouse-driven, with Command-clicks replacing the PC version's right-clicks:

    Click to tell your Lemmings where to go and Command-click to tell them where to shoot.
    To form Lemmings into a group that moves and shoots in unison (or to split up an existing group), click on one or more Lemmings (or their status bar panels) and then give them a new destination.
    Each group has a leader, indicated by a star under their feet. The active group's leader, whose star is filled, will be the one to collect or interact with any objects that you click on. To make a different group member the leader, Command-click them or their panel.

Keyboard shortcuts are also available:

    The 1/2/3/4 keys appoint a group leader.
    The 7/8/9/0 keys make Lemming 1, 2, 3, or 4 use a balloon if they're holding one.
    The left and right arrow keys switch focus to a different group.
    F4 toggles the window between 320x240 and 640x480.
    P pauses the game.
    The arrow keys and Return/Space can be used to navigate menu screens.

To unlock all levels, use this cheat code as a level password: 9913454278

The game insists that the CD be inserted every time you play, but mounting the ISO with the Virtual CD/DVD-ROM Utility is sufficient to fool it.