Calculator

Even the basic edition of Windows includes some basic features which aim to provide flexibility in most domains of activity. Among others, there's a calculator with a scientific component for complex operations. There are also third-party alternatives like Calculator which provide a different interface in case the default tool doesn't quite suit your style.

Offers a simple, colorful interface

For starters, the application comes in a lightweight package, saving you both the time and effort needed to go through the steps of an installer. This makes it possible to store it on a thumb drive to use on other computers. Just make sure that the target PC is equipped with .NET Framework, otherwise the program doesn't work.
As far as the visual design is concerned, the application comes with a colorful interface, with a calming background, and different tints used for every button. You find a general keypad besides the general set of operations you can perform. Needless to say that the upper part is fitted with the results screen, which also shows characters as you add them.

Leaves much to be desired

Input can either be done with the mouse or the keyboard. However, using the keyboard needs to be done with care, because the input field accepts all kinds of characters, which can result in error. What's more, operators need to be selected from the interface, because inserting them through the keyboard doesn't properly read them, and you're not able to obtain a result.
Sadly, the application is fitted with a pretty poor variety of features, and doesn't even match what Windows provides by default. You only work with basic operators like add, subtract, multiply, and divide, with no scientific components. There isn't even a memory slot to store results for later processing. Exporting is only done by manually copying the provided value.

In conclusion

To sum it up, Calculator comes with good intentions, aiming to be a cool replacement for the default counterpart. However, it only delivers basic operators, and isn't even able to be a worthy competitor for the Windows tool. Unless you only need to add, divide, and so on, you're sure to look for alternatives after the first run.