The open worldness of it all made it a bit difficult.
Halo Infɪɴɪᴛe's ᴄᴀᴍᴘaign mɪssiᴏɴs wᴏɴ't ʙᴇ repʟᴀʏᴀʙʟᴇ unʟᴇss ʏᴏᴜ stᴀʀᴛ a ɴᴇᴡ sᴀᴠᴇ file, a Microsᴏꜰt sᴘᴏᴋᴇspersᴏɴ hᴀs cᴏɴfirᴍᴇd.
Previous Halo games would let you jump between different missions from a select screen, being able to play each one individually as many times as you'd like. It was a quick way to tinker around with different difficulties and add skulls, but Halo Infinite's open world makes things a bit different from the older games.
While Infinite's map is mostly open and available throughout the entire game, the game's first two missions take place off Zeta Halo, with many other taking place in inaccessable parts of the map. You can't return to these once you've completed them, meaning that any collectables missed are gone for the rest of the save.
Skulls and armour cache unlocks are tied to your account so they won't disappear when starting a new save, but it's still a bit frustrating that you'll need to start from scratch if you missed an in-mission collectable halfway through the game. Any collectables outside of main missions should still be knocking about in the open world for you to grab anytime, though.
"The postgame does give you the option to keep exploring the wider environment, but for missions like the first two, where you're not on the ring yet, you can't replay from the same save file," the spokesperson told Polygon. "You'd be able to get any remaining FOBs, targets, [and] audio logs, but the main story missions would not repeat."
Nat Clayton had a good time with Halo Infinite's campaign, but felt that the whole thing was frustratingly close to greatness. "Halo Infinite is a strong return to form, and in the heat of battle it's the best running and gunning the series has ever had," she wrote in PC Gamer's review. "It's painfully easy to imagine a world where Infinite could have easily been one of my favourite entries to date. But between an open world that feels largely redundant and a story that can't shed the series' baggage, Halo Infinite's campaign falls just shy of being great Halo."