Energy and Body Parts

Energy and Body Parts

Documentation baseline: v1.1.126.

Each droid in OpenCaptive has an energy system and six body parts that affect combat survivability and equipment.

Droid Struct

The Droid struct is 68 bytes:

typedef struct {
    char    name[16];          // null-terminated name
    int16_t hp;                // current hit points
    int16_t hp_max;            // maximum hit points
    int16_t energy;            // current energy
    int16_t energy_max;        // maximum energy
    uint8_t body_parts[6];     // equipped item ID per slot (0 = none)
    uint8_t body_part_hp[6];   // condition per slot (0 = destroyed, 255 = perfect)
    uint8_t weapons[2];        // left/right hand weapon ID
    uint8_t items[10];         // inventory slots
    uint8_t skill_levels[10];  // per-skill level (0x00 - 0xFF)
    uint32_t xp;               // experience (max 0xF8FFFFFF)
    uint16_t weapon_damage;    // lo*hi encoding from original address 0x9BF4
} Droid;

Alive Check

There is no active field. A droid is alive when hp > 0. Dead droids (hp <= 0) are skipped for movement energy costs but remain in the party.

Energy System

Regeneration

Energy regenerates at 1 point per approximately 5 seconds (every 300 game ticks) for each alive droid. HP also regenerates alongside energy at the same rate (+1 HP per tick if below hp_max).

Consumption

Action	Energy Cost
Weapon shot	3 per shot
Movement step	1 per alive droid
Battery use	Restores 50 energy (ENTER key)

Dead droids do not consume movement energy.

Initial Values

New droids start with:

• HP: 100 / HP max: 100
• Energy: 100 / Energy max: 100
• XP: 1024
• Weapon damage: 0x050A

Body Parts

Each droid has 6 body part slots:

Index	Slot
0	HEAD
1	CHEST
2	ARM
3	LEG
4	FOOT
5	HAND

Body Part Condition

Each slot has a condition value in body_part_hp[6]:

• 255: perfect condition
• 0: destroyed
• Displayed in the droid UI as a color-coded percentage

Combat Damage

When a creature attacks, it damages a random body part. The damage to the body part is 1/4 of the attack damage dealt to the droid.

Armor Defense Values

Body armor provides damage reduction based on slot:

Slot	Defense Value
Head	10
Chest	15
Arm	8
Leg	8
Foot	5
Hand	5

Actual damage reduction scales with the body part's current condition -- a damaged armor piece provides less protection.

Repair and Installation

• Shop repair: restores all body part conditions to 255.
• Inventory installation: pressing ENTER on an armor item in inventory installs it to the appropriate body part slot, resetting that part's condition to 255.

Equipment

• body_parts[6]: stores the equipped item ID for each slot. Item ID 0 means empty, item ID 1 is the default starting armor.
• weapons[2]: left and right hand weapon IDs.
• items[10]: general inventory slots.

Environmental Damage

Hazard	Damage Formula
Pit fall (Captive)	5 + current_level * 2
Industrial hazard (Liberation)	5 + mission * 2

Droid Configuration Screen

Entered via STATE_DROID_CONFIG before the first mission. Displays all 4 droids with their stats and equipment. Controls:

• R: rename a droid
• S: swap weapons between hands

Initial droid names are generated procedurally using captive_generate_name with seed 42.

Source Files

• Droid struct and game state: include/game_state.h
• Game state initialization and logic: src/engine/engine.c
• Combat and tick logic: src/main.c