Combat is one of the most popular ways games allow players to express any kind of agency today. Great encounters can be found on both sides of the spectrum (linear vs open), but what I love about sandbox design is the players ability to tell a story within a story. Using Far Cry 3 as the continued example, while the overarching plot was debated plenty, it was the second to second experiences in the outposts that I walked away from with great stories, because there’s a sense of authorship there. Sandbox encounters lend far more tools to the player to author stories, and those are the events that I find I really engage with. When I built sandbox encounters I often compared it to building multiplayer levels. We always ensured there were opportunities for ranges of play styles, ways to assess threats, crossfire opportunities, refuge spaces to retreat to and reassess, recovery spots and ways to drop in and out of stealth. We also used techniques like “bait” to encourage certain kinds of play, for example, red barrels that are stacked next to a vehicle patrol route can be seen from the level entry vantage point. Along with all that you have to have a well defined goal and robust enough mechanics to let the player surprise even the developers.