Submachine
I love point and click puzzles. The Submachine is a great series. Start out on the first and learn how the author thinks, then work your way up. Submachine 4 is definitely tricky. Walkthroughs are available online if you get stuck.
Submachine
Submachine 2: The Lighthouse
Submachine 3: The Loop
Submachine 4: The Lab
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Submachine
Submachine 2: The Lighthouse
Submachine 3: The Loop
Submachine 4: The Lab