The movie Cube, the TV show Lost and, Portal are all broken down and reassembled in CUBE, a Half-Life 2: Episode Two mod about self-assembling test chambers. Unsurprisingly, I spent a lot of time stuck, but in a good way. CUBE’s an odd one: accomplished and beautifully designed in most respects, but always on the cusp of crashing. Engine errors are as ubiquitous as new puzzles. I'm still working my way through it: there's hours of content and multiple endings to complete, but it’s worth picking up and persevering if you miss Valve’s elaborately designed roomy puzzles.
I’m barely going to touch on the puzzles– they’re tricky constructs to divulge, and you should come into them fresh, but the world and mechanics are worth discussing. Cube and Aperture Science are the main touchpoints, here. You begin in that blocky, locked room of the movie. It initially feels directionless, but the clues are there to help guide you from the space into the larger, more involved test chambers that follow on from Aperture Science.
The chambers begin obliquely: the world’s made up of blocks, some of which are buttons that you need to press. They look just like the rest of the world, so there’s a fair amount of running and hitting the ‘e’ button to see what happens. It might sound stupid, but the rewards are watching a wall slide back, reassembling itself as a welcoming doorway for you to enter, or finding a secret door that leads you to an easter egg.
The first few real puzzles are block and button combos: ponder the space, ponder the cube, ponder the button, look around a bit before... success! Like Valve’s puzzles, it’s the slow drip of new ideas that keeps it from being stale: floorways with certain spaces to stand, gravitational fields that let you float to platforms, eventually the Gravity Gun They all combine with the moving walls, building features and escape routes right in front of you.
Like Portal, the walls are graffitied with warnings from past subjects, confused warnings of a future death awaiting you. Sometimes they're helpful, like the skull & crossbones outside a chamber that's insta-kill, and sometimes they're not, like the like a skull & crossbones outside a chamber that's at first appearance insta-kill, but eventually resolves into a simple puzzle.
It is broken, though: it crashed a few times in a way that I had to use console commands to skip but that the developers have promise to fix. And there's controversy on the ModDB pages about a few pieces content being lifted from other mods: it was initially removed from the site altogether, but it's now back, hopefully resolved. I hope so, as it's an excellently designed mod.