Super I-Frames, Giant Bosses, and Letting Players Cheat a Little

I just got back from Shmup Slam 8, and I've been talking, watching, and chatting with all manner of Mother Shmupper lovers.

Super i-frames are not just mercy. They solve a feel problem for normal players, but they also create a tactical optimization window for deeper strategies for players digging below the surface of the experience that you should design for and abuse as a player. Just don't design them as the only way to get through parts of your game. That's a bit of an asshole. I hate players' down-the-hole move.

In Interstellar Sentinel (IS), that means 2.4 seconds of safety during super is not only there so players don’t die during the cool explosion. Designing an all-powerful screen-filling explosion that you die in is bad juju. It also lets them do something risky, greedy, and intentional with giant boss sprites and positioning.

Most players use supers or bombs defensively. It takes skill, muscle memory, and reaction time to save yourself. After players get better with those skills, they graduate to waste-not, want-not. If you have a super powerup on screen and a full super meter, why not use your super?

At that point, it becomes an opportunity to put out more wanton destruction and create bigger gameplay moments.

In my games, the Interstellar Sentinel series, I also want you to wield the super like a giant multiple-death-screaming-enemy-soul-explosion beam that would make any Ghostbuster want to diddle the Containment Unit.

And by that I mean: stick the super into the boss’s face, pull the trigger, and use those i-frames to fly through it.

Mercy first, because dying during a super sucks

One of the funny little game design things I keep thinking about is super invincibility.

In Interstellar Sentinel (IS), when you fire off a super, I give you 2.4 seconds of i-frames.

Part of that is just basic mercy. If the player hits the big “make the screen explode” button and then dies during the big “the screen is exploding” moment, that feels like trash.

Not hard.
Not fair.
Not “skill issue.”

Just bad design.

And yeah, I’m a game director. My job is to call out bad design, including my own. Dying during a super is one of those things where I look at it and go, nope. Dud game design. Fix it.

But that’s only the first layer.

Then mercy becomes tactics

Most players learn supers as survival tools first.

That’s good. They should.

The screen gets ugly, your hands get a little stupid, something horrible is happening in the corner, and you hit the big button because you would like to continue playing the video game. It takes me ages to refine the reflexive muscle because I am fighting my hoarding, save the resource at all costs in case I need it mentality...

Perfectly valid.

But once the player gets better, the question changes.

It stops being:

“How do I not die?”

And starts becoming:

“How do I use this without wasting it?”

That’s the good stuff.

In a shmup, the whole screen is basically arguing with the player about space. Bullets say don’t stand here. Lasers say leave now. Boss bodies say absolutely not. Walls, enemies, attack lanes, weird organic meat nonsense, all of it is pushing and pulling the player around.

Then the super happens, and for 2.4 seconds, the rules bend.

Not forever.
Not enough to turn your brain off.
Just enough to let the player do something rude on purpose.

Giant boss abuse

With a giant boss sprite, i-frames are not just a safety blanket.

They are permitted to abuse the boss's body.

For a couple seconds, the player can shove themselves into places they normally should not be allowed to exist. Dive into the boss. Pointblank the damage. Tear through flesh regeneration walls. Turn the screen into a glorious mess of pointsplosions and potentially end in a bad decision if you overstay your i-frame welcome.

Beautiful nonsense.

That’s where the super stops being just a bailout and becomes routing tech.

A newer player hits super because they are about to die.

A stronger player hits super because there is a powerup on screen, the meter is full, the boss is huge, and wasting all that potential violence would be rude.

Same button.

Different brain.

Giant bosses are play space

Giant bosses are not just big pictures.

They are play space.

They have bodies. Parts. Collision. Weak points. Destructible chunks. Maybe some regenerating flesh wall nonsense because apparently I make choices.

So when the player gets a short invincible window, high damage, big score opportunity, and then the clean up of the stargem aftermath (bonus points that disappear if not collected), the boss becomes something they can exploit.

For a second, the question is not:

“How do I avoid this giant horrible thing?”

The question becomes:

“How much of this giant horrible thing can I get away with bullying?”

That’s good shmup stuff.

The balance problem

The trick is keeping the window tight.

Too much invincibility and the player stops respecting the screen. Too little and the game steals the cool moment from them.

Somewhere in the middle is the sauce.

You are safe, but not for long.

You are powerful, but not brain-dead powerful.

You are allowed to break the rules, but only inside the little window I gave you.

That’s the design space I like. A mechanic that solves a feel problem for normal players, but also gives stronger players a way to be clever little monsters.

Super as panic button.

Super as optimization.

Super as boss-body abuse.

Same feature. Different layers of play.

So yes, I give you 2.4 seconds of i-frames on super because dying during a super is dud game design. I also know this is nearly an eternity in the tightness of the best Cave shmups, but hey that's my sauce, and I'm happy to create a little more space to be discovered and abused, especially when it leads to crazy moments of scoring.

But also because I want you to abuse the giant boss sprite a little. I want you to figure out Daisy Chain Supers, big bullet cancels that nearly refill your super meter, and I want you to feel like you're the inner god eye of the machine when you figure it out.

Stick the super in the boss’s face.

Pull the trigger.

Fly through it.

Tactics.