If you like side scrollers, check out Rogue Legacy. The twist is all the heroes has disabilities that can affect gameplay, which is pretty comical. Things like ADD make you faster, or giantism which makes you... giant, or negative ones like vertigo which make everything upside down (worst one ever).
I approve of this message, though not sure if they've made a Mac Port yet?
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Nested:
http://indiegames.com/2013/09/browser_pick_discover_infinite.html#more"The interface is perfectly simple, which makes it easy to start playing and even easier to keep clicking away. The display is set up like a directory of nested folders. You click on a universe, which gives you access to a number of galaxies, each of which contains planets, asteroid belts, and such. You can click to explore planets, and if they harbor intelligent life, you can view the species and cultures, visit their museums, and even see their thoughts.
Or you can keep diving deeper, perhaps into the bones of a creature, or into the elements that make up a rock, then into the atoms and the quarks, and deeper still into an alternate multiverse. Fly inside a black hole, then through a white hole, and discover a hypoverse or a lasagnaverse or a sharkverse. Sift through the stars and see what universes are hiding within."