Released in 1985, the arcade game Commando was an exemplar of the style that Capcom embraced in those early days: It was simple, repetitive, and pretty to look at. You play as a little blue soldier named Super Joe, shooting down green soldiers in some generic jungle until there aren’t any more. Then a helicopter picks you up, and you get a message from the game: “CONGRATULATION YOUR EVERY DUTY FINISHED.” That was enough. Commando just needed to provide enough structure for players to keep putting in quarters. It didn’t need to stick to your bones. By 1988, when Capcom made Bionic Commando on NES, the studio knew that its games needed to be more than just a pretty lure for quarters. This was a longform game that you were supposed to finish. It needed a heart. The first place you can detect that heart is Area 5.

Bionic Commando was unusual but familiar. There was no shortage of games about gun-toting dudes wearing green military jumpsuits back in 1988, but unlike most of them, Bionic Commando’s Nathan “Radd” Spencer couldn’t jump. Instead, he had a grappling hook that he used for swinging over chasms and climbing up bases. Learning the hook’s weird rhythm through the first couple stages—on your way to rescue the old hero, Super Joe—is tricky and discouraging, but the process helps lends the game a distinctive character that it wouldn’t have otherwise. Those introductory stages are a bunch of caves, fortresses, and pits full of spikes, every bit as generic as Commando’s jungles.

Area 5 transforms Bionic Commando, galvanizing the entire game with unexpected trials and a somber air. Unlike the previous stages, which are just blue skies and dark interiors, Area 5 takes place at sunset, the background a wash of orange and pink mountains. Junko Tamiya’s score matches the shift, going from staccato military themes to a stirring, driving minor-keyed anthem. The whole scene is so convincing that the inherent silliness of a guy named Radd saving a guy named Super Joe slips away. Suddenly your task matters. It’s not just about getting to the end of the stage and making sure every duty finished, but also about saving a human being and stopping a real military threat.

The shift is more than an aesthetic change. Rather than send you to another cave or military compound, Area 5 has you climb an enormous tower still under construction. Before that, the grappling hook’s used only as a jump replacement. You may be using a different mechanism than Mega Man or Super Mario, but it’s pretty much the same principle of jumping over something right in front of you. Ascending the tower, though, involves grappling up smaller objects like lampposts—which are rounded, so you can’t stand on them—in order to grapple up to even higher tiers. The tonal shift toward desperation and resolve are mirrored in the physical effort.

You’re appropriately rewarded for getting through. Getting to the top and finishing off the milquetoast boss—yeah, there’s a bad guy up there, but the real “boss” is the tower—nets you a rocket launcher. More than just an upgraded weapon, it’s also the key for entering Area 6, a nighttime port stage that continues to raise the stakes of the grappling hook challenges, if not the emotional stakes. That ramp characterizes BC’s back half—big challenge, less emotion.

The heart’s still there, however, beating away under the surface, and it’s most present again in the game’s ending. After you save Super Joe and the two of you attack the enemies’ headquarters, the action climaxes with a gruesome depiction of a resurrected Hitler’s head exploding, and what follows are epilogue scenes that are celebratory but contemplative. A fanfare plays over an image of celebrating soldiers, but eventually the music fades out, and this message pops up on the screen: “Now, so much time has elapsed, and I’m old now. I think it’s time for me to tell you the whole story. I hope this story will be told for a long time.—2010.8.2 Joe”

That coda’s a far cry from “Congratulations!” It’s moving and means Area 5 isn’t an accident. Capcom struggled often with its Nintendo games, trying to find a way to make them more than the diversions that their first arcade efforts were. Endings were a good way to rethink the emotional payoff. And it only works because of the groundwork laid in Area 5, the place where that heart Capcom was trying to evoke beat the loudest. Just like Radd Spencer climbing the tower, Capcom was aiming higher.