Ikari Warriors/Game Mechanics

Ikari_Warriors_(NES)

Items

• F - Your bullets will be able to pass through walls and multiple enemies.
• L - Longer bullet range.
• S - Faster firing rate (bullets).
• B - Grenades will finish with a huge blast upon impact.
• SS - Your speed on foot is increased.
• Gun - Bullets are restored to 99.
• Grenade - +50 grenades
• Gas can - Bullets are restored to 99, +50 grenades, gas is restored to 99
• H - Bullets and grenades are restored to 99 and gas is restored to 199
• Knife - Touching an enemy inflicts damage corresponding to a bullet. Enemies that are immune to bullets will either be rendered harmless (for example the "big men") or will still kill you (helicopters and tanks). The knife also allows you to run through gates destroyable buildings.
• Heart - Allows you to keep all collected items if you die or clear the level. Without a heart, you'll start from scratch. Once used, you need to collect another heart.
• Golden heart - Same as the heart, but gives you all upgrades and replenishes your inventory to the max.
• K - Smart bomb, kill all the enemies on screen
• Various other items (girl, clock, gold box etc) - Points (useless)

Collecting several upgrades of the same kind does nothing more than add points to the total.

Movement speed

Diagonal movement in this game is done at a 45o angle on a flat surface. Slopes change this angle (more about this below). All levels go from bottom to top of the screen so it's important to keep the vertical movement speed up as much as possible. Below ratios are with respect to the foot speed with the SS power for the vertical speed (unless stated otherwise).
Diagonal/Straight speed ~70% (on a flat surface, regardless of in the water, in a tank etc)
Foot ~67%
Tank ~83%
Heli 100%
Foot (SS) water ~74%
Foot (SS) uphill slope ~70%
Foot (SS) uphill diagonally ~55%
Foot (SS) downhill (horizontal speed)^ ~121%
Foot (SS) uphill (horizontal speed)^^ ~61%
Foot (SS) diagonally uphill (horizontal speed)^^^ ~45%
Foot (SS) diagonally downhill (horizontal speed)^^^^ ~100%

^ It's not possible to move in a straight horizontal line on a sideways slope. You will lose 4 units of height for every 10 horizontal units.
^^ The opposite of ^.
^^^ You will gain 12 units of height for every 10 horizontal units.
^^^^ You will gain 6 units of height for every 10 horizontal units.

Some comments on how to use the above for speed considerations:

• Helicopter and foot (with the SS power) speed are equal and the fastest modes of movement.
• Diagonal speed is "geometrically correct". Since the diagonal movement is done at 45o, the speed ratio of ~70% corresponds to the inverted square of two as it should be. This also means that diagonal movement should be done when traveling at the fastest movement speed. For example, it's better to wait until you get out of the water to start moving diagonally.
• In water areas, it's slightly faster to walk uphill and then downhill again instead of staying in the water the whole time. This is very marginal though and only useful in level 4 (could possibly be used in the water section of level 3 with a new route).
  
  

Glitches

Flying glitch
If you hold A, B and up at the same time while in the helicopter (they don't need to start to be pressed down simultaneously, you just need to hold them down at the same time), Paul/Vince will exit the helicopter and continue traveling vertically at helicopter speed as long as A and/or B is kept held down (the glitch doesn't work with the tank). In this state, you're invincible, can't interact with anything in the game (such as collecting items or the terrain) and can't use your weapons. If you let go of A and B, you will either be teleported back to the helicopter (if it's still on screen) or land in a glitched state. Your movement speed will be back to walking speed, but the movement doesn't correspond to the graphical terrain (you'll appear to walk in water while on land, there will be invisible walls etc). You'll still be in the invincible state, you're still unable to collect items or use your weapons. The only way to revert back to normal is to exit the level. This glitch has the potential to completely break the game, but is of limited use with the current knowledge due to some unlucky circumstances: - In level 1 you still need to collect 3 items (SS, the knife and the heart) after the helicopter section. If you activate the flying glitch and fly through the whole level and exit, you will start level 2 without any power-ups. This saves 30-40 seconds (obviously depending a lot on what the alternative route was). As a strike of luck, the two most important power-ups, SS and B, are available very early in level 2, making it possible to start building up the character again.
- There is unfortunately no helicopter in level 2.
- Since you need to "fight" a boss at the end of level 3 and 4, activating the flying glitch here is essentially the same as soft-locking the game.

Some comments about various aspects of the game mechanics

• Airstrike target plates - Not dangerous themselves, they will trigger an airstrike when you get close to them. Sometimes the airstrikes come so quickly that it's literally not possible to avoid it. Sometimes it will take a while. The angle of attack is also different from time to time. The best way to understand this is to think of a steady stream of (invisible) bombers passing by from left to right. Their position when the target plate is activated determines the angle of attack and the speed. Once they cycled through from left to right (roughly 1000 frames), their distance will also be different. It hasn't been investigated how long time before the distance from the target plate is cycled back. While this information provides some understanding for what at first seems to be a random game mechanics, there is no known way to manipulate the airstrikes to not be undodgeable. The only way to mitigate the risk is to try and minimize the critical places where you have to travel next to or through these target plates.
• "Small rock face" (name taken from the strategy wiki in external links, although this certainly fits poorly with how it looks in the NES-version) - These shoot arrows horizontally through a small hole in the side. The interval between arrows is not understood, but arriving at different time windows (very roughly 100 frames) will result in different arrow patterns. There is lots of randomness with these enemies, but also some individual behavior.
• Entering a vehicle creates an immobility of around 1 second.
• Leaving a vehicle creates an immobility of only a few frames (seems to vary a bit, but less than 10).
• If you approach a vehicle while holding down the A-button (the grenade button), you will enter the vehicle on the first possible frame.