General Pacing Guidelines

In any mission or story driven game, pacing plays a big role, and a good level starts with a good pacing structure.
You don't want your level to feel flat and boring and you can't expect the player be at
200% tension level for hours.
More than that, it's contrast in your pacing that will make the powerful moment even more powerful.

There are countless ways to arrange the pacing of a level, and the game blueprint / narrative will of course drive the experience, but unless you are following something special, you can rely on the following structure as a base.

ABOUT OBJECTIVES
In a traditional story driven game, objectives not only guide the player, but they are directly link to gratification and the feeling of accomplishment.

Two simple guidelines here : don't make it too long, and keep it clear and simple.

• LONG TERM OBJECTIVE - 45 mins max
  They are usually key objectives leading to some big adventure progression step.
  They are long enough for the player to feel like they've done something and long enough for the game to deliver a lot of experience.
  i.e. Destroy the nuclear weapon factory (35 mins)
• SUB GOALS - 15 mins max
  Those are the sub steps of the Long Term Objective, delivered in bite size format.
  They are short enough so the player is constantly feeling like "I'm alost done...just a couple more minutes".
  Sub Goals will drive the player AND provide small victories/gratification for the player.
  Note that sub goal should individually follow the same pacing structure : Exposition > Build Up > Climax > Breath!
  i.e. Infiltrate the factory perimeter (5 mins) // Sabotage the power generator (10 mins) // Place explosive Charges x3 (10 mins) // Free the Prisoners (5 mins) // Blow up the factory (5mins)

TYPICAL TENSION TIMELINE

Exposition

• Safe Place to present the next objective
• "Sell" what's coming next

i.e. In our "Destroy the weapon Factory" example, we could find our player gliding from a parachute and landing close from the facility while being briefed about the mission.
The player would then have to deal with patrols, find a breach in the wall, kill sentinels and get in.
In this exposition section, we can build up on the same curve and our climax would be the fight against sentinel while a safe place would be available right after you break in.(--> get inside the perimeter through a building, good for streaming...good for pacing ^^) Notice the sense of accomplishment when you get inside and the sub goal updates itself.

Opposition

• Damn it! Bigger problems than expected...
• ...but wait...there's a solution
• This is where the mission core gameplay begins

i.e. In our example, we would discover that the factory is protected by heavy automated turret, requiring an extra step : cutting the local power generator to ease things a bit.
Player would have to fight it's way to the generator (side building) before destroying it.
Again, build up as you fight to reach the protected generator, and brief moment of calm when you destroy it. (sense of accomplishment upon destruction)

Spice Up / Ramp Up

• Player is now familiar with mission core gameplay, time to shake him up!
• Let's introduce some new challenge / gameplay modifier / more difficult setups

i.e. In our example, we could introduce a new Shield enemy + blockades choke points protecting the bombing sites. --> need to adjust your tactics a bit to defeat the new NPC + sense of accomplishment every time you pass a choke point and place a new explosive.

Climax

• Make the player feel it's spiralling out of control...
• ...you reach a tension plateau
• Should be short and powerful

i.e. In our example, right when the player triggers the last bomb timer, he learns there are friendly hostages being held in the facility.
There are just a few minutes left to free them and protect them against waves of enemies while the bombs you placed detonates one after the other.

Breath!

• Backt to safety : player needs to catch his breath...
• ...and get emotionally ready to face next challenge.
• It's important to get back to the lowest possible tension.

i.e. In our example, you barely made it alive to the extraction chopper...but can relax a bit as you fly away in the dying sunlight over the sea ^^ Mission accomplished!
But wait...what's this red dot blinking on the radar ?

The overall curve would probably look something like that.