Developer: Pomegranate Software
Price: $19.99
Version Reviewed: 4.0.4

Utility Rating: ★★★★½
iPhone Integration Rating: ★★★½☆
User Interface Rating: ★★★☆☆

Re-use / Replay Value Rating: ★★★★☆

Overall Rating: ★★★★☆

SpaceTime is a calculator.

Actually, scratch that: it’s more like a machine. A TI-89, for those of you familiar with graphing calculators—except that while it lacks the 89’s larger interface, it can actually do more. All of its features are crammed to fit onto this tiny screen, but the resulting app’s abilities are very impressive indeed. Plus, SpaceTime costs just $20. That might be expensive in the context of the App Store, but compared to a $80 graphing calculator, it’s ridiculously cheap. The only drawback is the iPhone’s screen size, but iPad owners should check out the (separate) SpaceTime for iPad app.

Though this is an in-depth review, it’s still impossible to cover every feature in this app. If you have any specific questions, please leave a comment below!

So What Does It Do?
Perhaps a better question is what doesn’t it do. You can plot 2D and 3D functions; perform complex differentials and integrations; find limits; perform matrix calculations; and do all the “simple” math operations such as calculating nPr (probability), trig values (the usual suspects, including cosh and sinh), and exponential calculations. Basically, SpaceTime can do almost anything. Over 200 functions are built into the catalog, and its abilities rival those of Mathematica and MATLAB.

Building upon SpaceTime’s robust capabilities is a scripting option, where you can write your own “scripts” using SpaceTime’s unique coding language. These can range from simple—a quadratic equation solver, perhaps—to a script that draws a graph. The functions possible are essentially limitless.

The Interface
SpaceTime’s interface is initially daunting, but an exhaustive tutorial system teaches you how to use it. The bottom half of the screen is a custom keyboard, with basic numbers and trigonometry functions as well as the variables x, y, and T. The Plot, Entry, and Solve buttons are also here. Tapping the boxed “1” in the corner reveals a more complex keyboard, this time with symbols for integration, logarithms, and other functions. If you can’t find the symbol or command you need, chances are that it’s in the Catalog, which can be opened from the top of the screen.

The top portion of the screen shows your current expression as well as previous lines, much like a normal graphing calculator. You can scroll through your previous entries at any time. If you’re entering a large, complex query, there’s a separate screen for you to do so.

For graphs, you can double-tap them from the top portion, and you’ll be translated to a custom graph screen. The functions of this screen are dependent on the type of graph. For example, for a 2D graph you can view minima, maxima, zeroes, and intersections; a table of plotted points; or trace the lines of the graph. 3D graphs allow you to rotate, zoom, and turn. Getting out of the graph screen is a bit confusing…you have to double-tap on the graph itself again.

Practicalities
As I mentioned above, SpaceTime is a super-calculator. It can do just about everything.

Then again, so can a TI-89…and that calculator will even play games or read text files, if you’re willing to play with it. Where exactly does SpaceTime fit into your life?

Actually using SpaceTime is difficult at first. There’s a significant learning curve, and it’s easy to make mistakes with the custom keyboard. Eventually, however, things become easier. You learn where the buttons are. You adjust to SpaceTime’s slightly-different syntax. The typos might remain a problem, but at least you can use SpaceTime efficiently.

However, you won’t be able to move as quickly as you would on a real-life, dedicated graphing calculator. This is due to an inescapable physical limitation…the iPhone doesn’t have buttons, and the lack of tactile feedback forces you to move more slowly. I imagine that on an iPad’s larger screen, using SpaceTime would be easier; the UI would really benefit from more space. Pomegranate Software offers a separate app, SpaceTime for iPad, which iPad owners should check out.

On the other hand, SpaceTime is more flexible than most calculators. The scripting feature is powerful—though the TI series also supports “programs,” I found it easier to use SpaceTime’s language. 3D graphs are rendered beautifully, though you sadly can’t save the pictures for future reference or citation. In some aspects, it’s actually better than a graphing calculator—it has so many functions built in! It’s powerful enough that some have compared it to the computer program Mathematica.

And as an iPhone app, SpaceTime blows its competitors out of the water. It’s a workhorse, pure and simple. The tutorials, examples, and demo files included all do a superb job. I’ve yet to see any bugs in the app itself.

If you’re looking for a complement to a graphing calculator or aren’t sure whether you need one, SpaceTime is an excellent bridge. It’s highly functional, and despite its learning curve, it’s an excellent app. There’s so much value here if you’re willing to invest time and patience. In the App Store, SpaceTime is peerless. Even beyond, it’s still a strong contender.

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