TL;DR:
It's a neat game from a neat developer in a large, untapped game space. And it's cheap. If you've got a VR set, definitely buy it. If you don't, maybe buy it anyway.
Pros:
-Novel concept
-Mind-tickling
-Large problem space, lots of mechanics for the developer to explore
-Cheap
Cons:
-Simple
-Currently (3/17) doesn't encourage use of the time visualization component enough, which is the bit that should set this game apart
-The VR version crashed on me once when switching audio devices
Long, for those with trouble sleeping:
Way back in 2011 Achron exposed time as a navigable dimension. The analogy between time and spatial dimensions is stronger in Achron than in any game before and any game since. In Achron time is a freely navigable ~10 minute window that resolutely marches forward, as opposed to the zero-length window we're used to. While the game has (effectively) two spatial dimensions, time acts much like a third. In my utterly amatuer opinion two major wrinkles held Achron back - a sub-par implementation of RTS principles painstakingly perfected in other games, and immense complexity conveyed to the player in an unintuitive way.
Imagine if, instead of seeing a typical two-dimensional RTS map, you could only see one column of pixels at a time. You could freely navigate the columns, but you could not see all of them at once. Imagine how much harder it would be to understand the playing field, especially as the game progressed and the field changed. It is similarly difficult to understand time in Achron. The player must select and view each time slice, a single scene does not convey the whole space.
zTime takes the time dimension and visualizes it along a spatial axis (the z axis I presume, hey that's probably where the name comes from). You're on a two-dimensional obstacle course, and the paths of you and the obstacles are drawn over time along an axis orthogonal to the obstacle course. They appear as contiguous lines. By aiming your future-position line between the future-position lines of the obstacles, you can avoid them a few seconds in advance.
Even when projected onto a two-dimensional screen, the player can take in vastly more information about time when conveyed visually. The VR experience is an ah-hah moment as well. Seeing that third dimension with stereoscopic depth cues dramatically increases the fidelity of the information. zTime conveys time as a first-class navigable dimension in a way that Achron never could, because zTime is a simpler game.
Unfortunately, zTime eliminates the mutability of time. The player observes time as a navigable dimension (navigable by the eyes), but can only make changes in the current time slice. It's a little like Guitar Hero et al. in that way. The player can see the future, but must make changes in the present. The past is therefore irrelevant and not shown. The earth-shattering mind-bendy-ness of Achron is notably lacking in zTime.
After playing zTime for maybe twenty minutes I had only one "hey that was pretty cool" moment, where I navigated the obstacle course using the spatial representation of time more effectively than I would have used everyday prediction of the movement of the obstacles. In many more cases, trying to utilize the time dimension resulted in my death, where navigating the same obstacles without the fancy lines would have been trivial. All of the obstacles (up to level 11, at least) move in short-period repeating patterns (or just follow you), so they are predictable. When there are many obstacles to keep track of, the time visualization becomes helpful but not necessary. It seems like obstacles with random movements would make the time visualization more rewarding. With unpredictable obstacles, the player would be forced to use the visualization of the future to navigate the maze safely.
The developers made an interesting decision when deciding how to visualize the player's future position - your future-position line assumes you will maintain your current acceleration indefinitely. This makes predicting where you will be in three seconds easy, but makes it difficult to make small changes to your trajectory in the x/y/time 3D space. When you press a key to make a minor modification, your future line shoots off in that direction, and you must release the key to see where you will end up without input. It becomes a guess-and-check game, and you only have a few seconds. Using the Vive controllers makes this a bit easier because it has a high-resolution trackpad for movement, instead of the measly four keys on your keyboard.
Other minor gripes:
-there should be an obvious visual cue in future-position lines to indicate that an object hit and bounced off of a wall. The change in direction from the bounce is easy to miss
-viewport zoom is unbounded, which is amusing
-on the Vive controllers, the trackpad is used to navigate menus, but the trigger is used to click. The more common convention is to use the trackpad to click if you're using the trackpad to navigate
Final thought:
Personally, I think the developer missed an opportunity to pare down and polish Achron. Take that same time-bending engine, incorporate it into a simpler RTS built on a generic game engine, and you've got yourself a compelling modern game with all that mind-blasting goodness.
