What's really great about this series is its reliance on persistence. It's extremely easy to go into a tailspin dive where an unlucky roll of the dice can kill a squad member and you're desperately trying to scrape together enough resources and troops to stave off being flattened by aliens.

You can also enjoy 28 hours and 28 minutes of fun for $3 (£1.74) right now on Steam. It's also cheaper than the bus I used to get to work this morning, and I'm convinced much more enjoyable than public transport, which is why I'm going to be taking a bus to work in the next couple of weeks. [In particular, according to the June SteamDB price history, it sells for around $2.70 (£2.40), with similar discounts routinely offered.

Nevertheless, if you are really strapped for cash, FOMO may not be a bad idea. The base game has had similar discounts in the past year, but there is still a significant gap between this campaign and the offer, so you can't get it for significantly less than the price of a Big Mac, seven Fredos, or a fifth of a US subscription to World of Warcraft! It is a very month-to-month theory that you won't get it.