Grim city-building survival game Frostpunk (opens in new tab), which we named 2018's best sim (opens in new tab), is 50% off on Steam right now. It's $15/£12.50 (opens in new tab)—its lowest ever price, according to deal site IsThereAnyDeal (opens in new tab).
In Frostpunk, you slowly build a city in a frozen world that offers very few resources. It's tough, and miserable at times: you'll contemplate horrific decisions just to make it through the day, such as mixing sawdust into meals to bulk them out, or sending children to work in dangerous factories. Your citizens will often freeze, fall ill or starve, and if they're unhappy enough they can even banish you from your own city.
Chris sung its praises in his 89/100 review (opens in new tab), calling it a "stressful, stylish, and addictive survival management game filled with incredibly difficult choices". Once you've started a campaign, its very hard to tear yourself away.