Ikari_Warriors_(NES)

Level by level description

Level 1

Foot to tank - https://www.youtube.com/watch?v=mfIetUyC1aQ
If you start speedrunning this game, you'll see this section many times. This is where it becomes apparent that the game's rng must be fairly primitive. The enemy movements are clearly intended to be random, but you'll soon be able to correctly predict many of the movements. There are still many possibilities, so they will not be listed here.

Tank to foot - https://www.youtube.com/watch?v=p0SzRGjiPX4
The F and L are absolute requirements for the rest. The S is a nice to have, but not at all necessary. The first part of this tank is plagued by random grenade thrower spawns. They should only occasionally be able to hit you, but they're still an annoyance. The rest of the section is mainly to hope for not late tank spawns because of the sprite limit and getting the timing down to take out the gate guards without touching the gates. The shots during the last stretch before leaving the tank was to take all enemy soldiers approaching. If not, they will approach from behind and catch up with you while you're in the water on foot.

Foot to helicopter - https://www.youtube.com/watch?v=BcwUzhX_2Uo
There are only four enemies you need to care about here. They are all best taken care of with grenades as shown here. The first one is a machine gunner that will also home in on you. The next two are self-exploding guys and the last is the rapid machine gunner right before the helicopter. Maybe 5-10% of the time, the mine will kill you if you walk in a straight line. If you want to reduce that risk (at the cost of a few frames) you can slightly to the left when you're walking alongside it.

Helicopter/flying glitch to the end - https://www.youtube.com/watch?v=ylCHMOPwtU8
The flying glitch is described in the Game Mechanics section. Right before the end of the level, you teleport a bit forward. It's also possible to teleport backwards. This glitch hasn't been researched, so the details are not understood. However, if you leave the helicopter as early as possible, you'll get the forward teleportation near the end, which saves a few seconds.

Level 2

Foot to tank - https://www.youtube.com/watch?v=xpPSTUHsQVc
This part of the game is tricky even with all the upgrades because of many possibilities for random spawns. Starting without upgrades (because of not collecting the heart in level 1) makes it much harder still. The key areas where survival likely will have to take priority over speed is the open area where the SS is found (this place can be crawling with semi-aggressive blue soldiers) and the beach before the first water section. There are a few fixed spawns in the water that can be dealt with consistently by tossing a grenade just as you're about to enter the beach. Anything that runs on the beach usually means trouble though.c
The remaining part before entering the tank is a bit easier since you're fully upgraded, but there are still several possibilities for random spawns. Especially in the area around the arrow-shooting faces (up until the white structure), the enemies tend to be quite aggressive and it's worth stopping to take them out if you can.

Tank to foot - https://www.youtube.com/watch?v=yuFOPXwJbbw
This part is generally easy. There are only three trouble spots. The first is that the grenade throwers on the other side of the fortress sometimes get too close to you to get a grenade in. It's rare though (~5-10%?). When that is about to happen, it might be tricky to avoid since you don't want to destroy the blinking tank (because of the resulting explosion). The second one passing the gate. It seems to happen relatively often that the airstrike hits the target plate too fast for you to get out of the way. There is no really good way to avoid this (without further investigation on how the target plates work in more detail). Trying to go through in the middle is risky because of the arrows.c
It should be mentioned that it's ~1.5 seconds faster to go through the "labyrinth fortress" on foot. You can then enter the tank that is on the other side. However, that time gain can quickly be lost if you stop to take out any random spawns. Going on with the possibility of many random spawns is also risky. Entering the tank on the other side of the fortress also adds a risk because you will more often come into the range of the grenade throwers.c
It's theoretically possible to run through this whole section without using the tank, but the time gained by the faster movement speed is counterbalanced by having to stop to take some of the enemies and buildings in your path. Without resorting to strats such as dodging a rain of bullets, doing this section on foot or in tank is about the same, just much easier in the tank.c

Foot to the end - https://www.youtube.com/watch?v=UGAJAzgaTPU
You need to be very careful in the open area leading up to the "labyrinth fortress" and the fortress itself. There are many random spawn possibilities and they won't hesitate to shoot if they get the chance. Outside this area, this section is quite straight-forward as long as the execution is correct.c

Level 3

https://www.youtube.com/watch?v=-eGQLme7jFM
https://www.youtube.com/watch?v=mKlgpH833vA
https://www.youtube.com/watch?v=JdMkAsrR8xc
https://www.youtube.com/watch?v=hL9fAFnx5II
https://www.youtube.com/watch?v=YWbME65q8XU

Level 4

https://www.youtube.com/watch?v=P86cpDuYzw0
The first area before arriving at the pools is consistent. The most dangerous enemy is actually the pink soldier that comes from the top right. It might be worth to move a little out of the way to ensure his shot won't hit you. In the pool area, make sure you toss a grenade just as you are level with the start of the first pool. Keep holding down A (and B of course). This will take guarantee to take out the most important enemies. There can still be random enemy spawns that can kill you before there is time to react, but it's more of an exception. Overall, while this section looks tough, it's fairly consistent as long as you follow the path shown here.c

https://www.youtube.com/watch?v=DYI-ShDF8dk
If you carefully follow the path shown here, there should be no problems. There is only minor uncertainty with a sudden airstrike coming when going through the blue tunnels.c
This section would be extremely hard to do on foot.c

Foot to helicopter - https://www.youtube.com/watch?v=oqtI-QI1LE0
Random enemies can appear on the left side of the water section, but can quite easily be dealt with when it's the case. The rest is not random quite easy to execute. The route through the barrel area can be done faster and the big loop back before the helicopter obviously consumes a lot of time. However, from testing, this seems to give quite good chances for a fuel can drop near the helicopter. This has purely been tested by experimenting with various routes from various save states, but there is no hard proof that this optimizes the chances for the right drop. The drops contained inside the walls are determined a little before they appear on screen. By turning around and walking backwards, it's quite evident that the memory gets more and more corrupted. That's where the idea of the loop back comes from.

Helicopter to the end - https://www.youtube.com/watch?v=hCg_4BE0B0E
The last "missile turret" is very random and quite "intelligent" (moves in ways to avoid your shots), so care has to be taken here. The rest is fairly easy to execute. However, there is a small chance that weird things happen along the way. It can be enemies that spawn in slightly different locations and therefore being out of reach or a grenade that is tossed from one the walls that can hit. This is rare though. The route shown here is made to be as safe as possible (it's possible to take a straighter route at the cost of some risk), but it's still not 100% safe.