The combat system is strictly turn-based, as is common with this genre. You can take your time deciding what your next move will be, but bear in mind that your enemies will soon make their next move too. And most of these can be lethal.
In order to survive the dangers that you encounter, you have to use the members of your squad intelligently, making sure that they cover each other, destroying things in the way if it helps you, and, in general, using your head more than your marksmanship.
Steam Marines is a very fun strategy, role-playing and action game, which, in addition to offering a fun, interesting gameplay, also has a spectacular retro esthetic.