For many people, the Civilization series is the gold standard of turn-based strategy games. Civ V was a relatively simple 4X game you could win through military might or civil growth, and the ruleset expanded in Gods & Kings to increase your options with more military units, religion and espionage. The second expansion - Brave New World - introduces a slew of new game systems that both impact your game, and feel like they should have been there all along.
For those who haven't devoted 400+ hours to Civ V, it's important to point out the late stages of each game kind of dragged on - unless you were a jerk and went to war with every neighbor. Players who enjoyed playing peace-loving civilizations didn't have a lot to do beyond rushing the space program, or buying out city states. Brave New World makes the late game active and full of Sid Meier's famous "interesting decisions" for all kinds of players by adding a bunch of new systems. Trade routes, tourism, ideologies and the world congress all integrate seamlessly with the gameplay that was already there to make Civ V more addictive than ever.
Before, you achieved a culture victory by amassing the most culture points through constructing culture-earning buildings like Wonders, and building something called a Utopia project. Brave New World ditches the necessity to max out social policy trees and introduces a tourism score as a way to ensure your civ's culture influences all the others. The new culture victory is essentially a race to make your tourism score beat your opponent's culture score. Buildings and Wonders still generate culture points, but you accumulate tourism by displaying great works within buildings like museums or amphitheaters. Great works are created by Great Artists, Musicians or Writers, and you slot them into specific buildings. There's a fun minigame in moving great works around, and swapping them with your rivals, to get the best combination in your museum and earn the most tourism.
Once you discover the technology of archeology, you can also send out Indiana Jones-style units to dig up artifacts to display alongside works of art. Not unlike religion in Gods & Kings, managing your Archeologists becomes a fun balance between the logistics of getting them into foreign territory and not pissing off other civs for "stealing our cultural heritage." Pilfering too many artifacts from your rival can be just enough to force a conflict, and wars begun this way can feel organic and true to history.
Trade routes start fairly early in the game, and function automatically once you assign them to supply you with gold and science. Thankfully, you don't have to move the caravan units around yourself, but you do have to worry about raiding barbarians (and enemy civs) sacking your trade units, so it makes even peaceful, profit-minded civs have a standing army. The sea routes that open up later are even more lucrative, but are at risk without a strong navy. The economy is now balanced around the new income from trade routes, and it takes a while to understand how trade impacts your strategy, but it was great to see how trade routes dovetail with religion and culture by spreading both to connected civilizations.