100%

100%, which is most commonly referring to the 100% Item Completion speedrun, requires you to collect all 100 items before completing the game. There is one exception to this list which is the Varia Suit, because after defeating Charlie and receiving your fully powered Gravity Suit, you will automatically receive Varia at the same time if you don't already have it, and it counts towards your item percentage. All other 99 items must be collected as intended.

There are quite a few major routing decisions that are all roughly similar to each other in terms of times. Most of these routing decisions are decided based on difficulty vs consistency, or just preferring to do some speed tricks over others. The biggest routing decisions are:

• Early Brinstar vs Late Brinstar
• Ice First Norfair vs Newfair
• Powerbombs Door Clip vs Lottery

For a quick example of how viable each of the above decisions are, the current leaderboard has 1st and 2nd place doing completely different routes for all three of those decisions. Your time in 100% will largely depend on your movement skills and consistency and choosing one route over another will not necessarily guarantee you a better time unless you are better able to execute that route.

Near the end of the run is a trick known as Glass Tube which, if done correctly, will save time by avoiding some extra backtracking and room transitions. If you fail the Glass Tube trick you can choose to accept the timeloss and backtrack to gather the Etank, or you can continue past the item on what's known as the "Old Route" before the glass tube trick was found. This isn't so much a route choice but more of a recovery option in a racing situation to minimize the timeloss from failing the trick, but you can also choose to do this route if you have trouble getting the Glass Tube trick. It should be roughly about 10 seconds slower to go straight for the old route without attempting the glass tube setup at all. If you attempt glass tube, fail it, and then decide to switch to old route, you will lose that same 10 seconds plus the extra time you spent setting up for the trick.

One last major routing difference I will cover here for the sake of completeness is the HBJ route in Kraid's Area. This route will mainly be preferred in the Hard Mode version of this speedrun due to ammo differences, but it is still a viable route for Normal mode. The reason it's not included in the main list above is because it is much more difficult to execute this route optimally and there is hardly any time difference between this route and the much easier route in Normal Mode.

Brinstar

Every run will start off this way up to the Bombs item. After picking up the missiles behind Bombs is when you decide if you're going up to the Early Brinstar route, or back down for the Late Brinstar route.

Early Brinstar

The benefits for the Early Brinstar route is having the extra missiles for the Acid Worm fight and the extra health for the Norfair Heated Rooms later in the run. The major downside is this route requires three Infinite Bomb Jump sections that all need to be done quickly in order to stay on pace with the easier option, the Late Brinstar route. It is not only harder to just do all three infinite bomb jump sections without mistakes, but it is also even harder to optimize every bomb jump to maximize all of the time save in this route with Jump Bomb Jumps combined with maximum height bomb jumps.

This route is recommended for beginners only if they are able to pull off the bomb jumps with at least some consistency, and that they also have trouble with staying alive in the upcoming Kraid->Norfair sections of the run, because the extra Etank from this route helps make those sections easier to survive.

Early Brinstar Alternate Route

This map just illustrates the difference between the normal Early Brinstar route, and at the end of the yellow line you will finish the rest of Brinstar just like the other route.

There is a lesser used version of the Early Brinstar route that has the benefit of skipping the first Infinite Bomb Jump, meaning you only need to do the other two. The downside to this alternate route is you do not get the statue refill that you would normally get after the first Infinite Bomb Jump, which means you will still need to rely on some drop luck to have enough missiles for the upcoming Acid Worm fight.

This route is useful if you really need that extra energy tank from the Early Brinstar route but you have trouble with the infinite bomb jumps, and you're still farming or refilling before the Acid Worm fight anyways.

Late Brinstar

The Late Brinstar route immediately goes to Kraid after getting Bombs. This route has the benefit of not having to do those three infinite bomb jumps, but the downside is you will have less ammo for the Acid Worm fight so you will need to pay more attention to your missile count heading into Kraid. On a typical run where you're not slowing down to farm, you want to hope for at least 2 or 3 drops from the Zoomers starting after you grab the first Energy Tank.

You can mitigate the RNG a little bit by using some strategic statue heals. You can heal at the Bombs statue if you want to get it out of the way early, or you can wait and heal at the first statue in the game before you go into the Kraid Elevator Room as a slightly better/faster option.

The numbers you're looking for are at least ~22 missiles by the time you enter Kraid. You need a minimum of 30 missiles to kill the Acid Worm, and you will pick up two more missile expansions in Kraid before the fight which give you 10 more missiles. You will also need to use two missiles to open two red doors on the way to the worm, so 22 + 10 - 2 = 30 for the minimum. We'll go into more detail about pre-Worm ammo in the next section, so for getting through Brinstar just keep in mind if you have a missile count under 20 by the time you're passing the first statue in the game, you may want to take that refill to ensure a smooth start to the Kraid segment.

Kraid

There are two route options for your first visit into Kraid. Most of the time you will see the Normal route, and the HBJ route is usually only seen in Hard Mode because of the amount of ammo you have at this point. The trade-off for the two routes is the Normal route is much easier to execute while relying on some drop RNG to be fast, and the HBJ route is much harder to execute consistently. In Normal mode you should have enough ammo to kill the Acid Worm in two rounds, and compared to the HBJ route there isn't much of a time difference when you compare both initial visits and both cleanup routes later in the run. In Hard Mode you would have to spend more time fighting the Acid Worm and spending some rounds farming, which makes the HBJ route faster in that scenario.

Regardless of which route you choose, there is one missile pack in Kraid that requires Gravity Suit, Speedbooster, and Springball in order to do a ballspark inside the acid to reach the item, which means you will always have to come back and revisit Kraid at some point after defeating Charlie. There are some other items left behind even in the Normal route, because even though it's possible to get them now it's faster to grab them on the way through your required trip back through Kraid later in the run.

Normal Route

This is a critical point in 100% where you want to be mindful of your ammo going up to the Acid Worm fight, and also right after leaving it. You will need 30 missiles to kill the Acid Worm, and another 20 missiles to defeat two sidehoppers afterwards to open a locked door. You don't need all 50 missiles right away, but you want to have at least 20 when entering Kraid's elevator. You will pick up two missile packs before the Acid Worm which should bring you over 30 missiles, and you will get two more missile packs after the worm fight. This means you still need to get a few drops to have enough missiles to kill the sidehoppers, and with average RNG you can usually expect enough ammo. In a worst-case scenario you can expect to kill the first sidehopper with missiles and shoot the 2nd sidehopper from the safe spot, which loses some time but it won't necessarily lose you the run.

HBJ Route

The HBJ route is named after the difficult trick needed to skip the Acid Worm fight immediately after entering Kraid. After grabbing the save room missiles, you will need to do a Horizontal Bomb Jump over the acid and go straight to Kraid without collecting any other items. After defeating Kraid you will also need to recharge a shinespark in order to spark across the reo room and leave the area.

It is highly recommended to be doing this route only if you are also doing the Early Brinstar route so you will have an extra Etank to make up for the two Etanks you will skip in Kraid.