Ikari Warriors (NES)/Fuel drop manipulation
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Ikari_Warriors_(NES)
This page goes more in depth on how to manipulate fuel drops for the helicopters in areas 3 and 4. The RAM-addresses used here are listed in the memory address section.
Some background about object allocation in the RAM
All objects that aren't part of the background are allocated to RAM-address $500 and onwards (player 1 is always in $4FE and player 2 is always in $4FF, but they can be disregarded here since they don't interfere with the foreign objects). This includes enemies, destroyable structures, hidden items, mines etc and even bullets). These addresses are referred to as "object addresses". The object address with index 0 corresponds to $500, index 1 corresponds to $501 etc. A new object entering the screen will be allocated to the lowest available index and when an object leaves the screen (regardless of how), the corresponding index will be restored to null. Dropped objects will retain the address of the initial object through. Bullets are also an exception as they will be allocated to an index further down (without interest for the topics of this page).
Different objects provide different values to the object addresses. Some objects share the same value, so there must be additional addresses that determine the exact type of object. However, these values aren't overly important to know, but are helpful when analyzing emulator movie files. Below are some common values (but the list is nowhere near complete):
| Object address value | Description |
| (128) | Player moving forward |
| (120) | Player in tank/heli |
| (64) | Rail turret, drops, mine |
| (63) | Exploding rail turret |
| (62) | Soldier, heli, blinking object |
| (61) | Dying soldier, exploding barrel |
| (58) | Returning soldier, missile target plate |
| (54) | Guardian soldier |
| (53) | Dying soldier (alternating with 75) |
| (50) | Missile target plate with incoming airstrike |
| (45) | Dying kamikaze (alternating with 83) |
| 2 | Helicopter/tank in use |
| 64 | Unrevealed mine |
| 66 | Object not on screen (includes unrevealed hidden items and destroyable structures with drops) |
| 75 | Dying soldier (alternating with -53) |
| 83 | Dying kamikaze (alternating with -53) |
The type of drop is determined by the value of the object's "drop address". The drop addresses start with $0676. When the object leaves the screen, the drop address isn't reset to null, like the object address. When an object is allocated to an object address, its "drop address" can be overwritten with the object's corresponding drop value. This drop value is overwritten for most objects (including many objects that don't drop anything), but for example blue soldiers don't overwrite the drop values. The only drop value of interest is 20, which means fuel will be dropped.
Area 3 fuel drop
This section will explain how to increase the chances of getting a fuel drop from the first tank in the helicopter section. The tank drops in this game are determined by the RAM-address the tank object is allocated to.
