GD: Life Force (AC/JP) Rank System

[clymax]

A. Intro and Motivation

Spoiler

• So, Life Force (AC/JP) is my current project in terms of modding in fanmade achievements. After repeated setbacks, I finally managed to break through earlier today in figuring out the rank system via reverse engineering.

• I decided to make this post because nothing appears to be documented for Life Force as far as rank determination is concerned. This post comes on the heels of a similar post I made for Gradius II (AC).

• These are my preliminary findings. As such, they may be incomplete. If you find something not mentioned, and you'd like to share it, please feel free to reply here or contact me via PM.

B. Rank System

Spoiler

1. Overview

The rank of this game appears to be determined by an addition of different components.

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Lookup(Difficulty, Loop, Stage) + Powerups + Limiters = Rank

• The gameplay difference between rank levels increases as you reach the higher ranges: 21->22 is a larger deal than 5->6, for instance.
• Deaths per se do not appear to have an effect on rank.

2. Difficulty

This is set on the DIP switches.

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1. Easy
2. Normal
3. Hard
4. Hardest

3. Lookup(Difficulty, Loop, Stage)

This component is determined based on the following table (WIP). No idea why Normal and Hard are showing the same values so far. But I will update this section if I find out.

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Loop____Stage______________________Easy________Normal__________Hard_______Hardest
1       1 Stomach Muscle Zone         0             0             0             1
1       1 Boss (mid-fight*)           0             0             0             2
1       2 Kidney Zone                 1             1             1             4
1       2 Boss (mid-fight*)           2             2             2             5
1       3 Stomach Inner Chamber       2             3             3             7
1       4 Liver Zone                  4             6             6            10
1       5 Lung Zone                   7             9             9            13
1       6 Brain Area                 10            12            12            16
1       6 Brain Area - Moai+         11            13            13            17
2       1 Stomach Muscle Zone         3             5             5             9
...     ...                         ...           ...           ...           ...
2       6 Brain Area - Moai+          ?            17             ?             ?
3       1 Stomach Muscle Zone         ?             8             ?             ?
...     ...                         ...           ...           ...           ...
3       6 Brain Area - Moai+          ?            19             ?             ?
4       1 Stomach Muscle Zone         ?            11             ?             ?

* Approximately three-quarters of the way through the boss fight.
+ The rank doesn't increase mid-fight against Big Moais.

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Highest effective rank in first loop on Normal
13 + 8 + 8 -3 = 26

4. Powerups

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1. Speedup:  +0 (no effect)
2. Missile:  +0 (no effect)
3. Pulse:    +0 (no effect)
4. Laser:    +0 (no effect)
5. Multiple: +2 for each (max is four multiples)
6. Shield:   +2 for each (max is four shields)

However, note the Powerup Limiter described in the next section.

5. Limiters

On the first loop, the player is allowed some leeway in powering up without increasing rank.

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1. Powerup Limiter - Powerup component is reduced by 3 on the first loop.

This reduction doesn't apply to higher loops. Also, this component can't go below zero.

So what does this mean? You get your first Multiple (or Shield) for free. You can get one more (Multiple or Shield) for half the rank-increasing effect. Additional ones will carry the full effect in terms of increasing rank.

Moving on, rank is sampled and updated at all times.

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2. Rank Limiter - Rank is limited to 31 on any loop.

There isn't any stricter limiter for the first loop. Also, rank can't go below zero.

6. What Rank Affects

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1. Enemy speed
2. Enemy bullet firing aggression
3. Boss behavior

Enemy bullet speed does not appear to be affected.

7. Sample Calculations

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(Normal, Loop 1, Stage 1), Missile, Multiple x3
0 + 0 + 6 -3 = 3

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(Hardest, Loop 1, Stage 5), Missile, Pulse, Multiple x4, Shield x4
13 + 0 + 0 + 8 + 8 -3 = 26

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(Easy, Loop 2, Stage 1), Laser, Multiple x2, Shield
3 + 0 + 4 + 2 = 9

8. Multiplayer

• The rank doesn't increase from the per-se addition of a second player.
• As for powerups, the calculation is the same as described above. Note that the maximum of 4 Multiples and 4 Shields applies to the total of two players when playing in multiplayer.
• This means that if Vic Viper has 3 Multiples, then Lord British can only get 1 Multiple at most. And if Lord British has 2 Shields, then Vic Viper can only get up to 2 Shields at most.
• This results in a high degree of parity with single-player mode, in terms of rank determination.

C. Acknowledgements

Spoiler

• Youtube's SuperViperT302 for some hints to keep me motivated to track down the rank value when I was getting discouraged from the wall I was running into.

• As one might suspect, these kinds of posts of mine were originally inspired by Seahawk's post here. Not only that, but as with my previous post, the structure of this post was humbly but shamelessly taken from Seakhawk's post. As such, credit for the structure goes to Seahawk.

[BIL]

Great threads! Supremely useful to have this data on hand.