FDD
Table of contents
Table of contents
Preamble - about the doc & boss
Setting & Character
Echidna (and Snake)
Erebus
Fight
Hades as avoidance-based System / Design Goals
Combat Design Pillars
Challenged Skills
Actors
Boss Movement
Level Requirements
Phases
Intro Sequence
Phase 1
Start
Attacks
End
Phase 2
Start
Attacks
End
Phase 3
Start
Attacks
End
Phase 4 - Outro
Start
Attacks
End
Loot
Pacing
Beats, Scenes, Sequence
Visual Requirements
Echidna
Snake
Feedback & Telegraphing
Animation Sequences
VFX
Sound
Rejected
Homing magic missiles
Summons (Slammer Hydra Head, Summoner Hydra Head, Cerberus)
Preamble - about the doc & boss
The Feature Design Document focuses more on combat design than full integration into the other game systems.It is fully from the System Design point of view and assumes that the Core Gameplay and Zagreus' general abilities are known and that they do work. It does not go into detail of work to be done by other departments and only outlines the requirements the Combat Design has for those departments, leaving space for their work.This document only describes the Echidna's moveset, background, and details important to the Combat Design and Game Feel. The structure is meant to showcase the full fight sequence from the Player's perspective to understand the flow of the phases and information shown to the Player. That means it's not fully broken down into workable chunks like the 🖥️Engineering document.
Setting & Character
Echidna (and Snake)
Children of the Echidna are, inter alia, the Cerberus, the Hydra, and Gorgons, though sources vary.
Some myths say she is immortal while others say she was killed in her sleep by Argus Panoptes , the hundred-eyed giant who served Hera. Her mate Typhon challenged Zeus and was thrown directly into Tartarus by him.
The Echidna is described as half beautiful woman, half fearsome snake, either from the waist ("snake-legged") or from the head down.
In one version of the lore, her snake tail is said to eat raw flesh, suggesting the tail actually ends in a snake head.
Erebus
Fight
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Hades as avoidance-based System / Design Goals
As an avoidance-based system, Hades' combat focuses on reacting to the enemies' attacks and finding the opportunity to strike back and deal damage. That means while each attack and attack combinations can be designed to be tricky, they also have to have a certain amount of down-time that allows the Player to progress, bit by bit, and they must be consistent for the Player to memorize them and react to them strategically.
Combat Design Pillars
React
Attack
Recover
dodge, block, reflect, dash
normal, special, call, lead into traps
time to refocus and prepare, possible health drops
Challenged Skills
Physical
Mental
reflexes
timing
muscle memorization
precision
endurance
regularity
concentration
memorization
observation
positioning
prioritization
tactic
pressure management
cost-reward analysis
multi-tasking
Actors
from this point, I will refer to the actors as follows:
"Echidna"
- refers to the humanoid part of the boss
- wields magic
- can summon creatures
"Snake"
- refers to the snake headed tail part of the boss
- attacks Zagreus with strikes and leaps
- can spit poison
Summons
- summoned by the Echidna
- Wave Hydra Support Head
- Magma Spittle Support Head
- Gorgon
The Echidna and the Snake share a health bar.
Total Health
1600
Boss Movement
The Echidna is a mostly stationary boss. She has one spawn point and moves slightly around said point. During some Snake attacks, the Echidna is inactive as the Snake takes control of the whole body.
The Snake part changes location during some attacks.
Level Requirements
Requirements change with each Phase.
→ The level structure can change for the different phases.
The fight takes place in Erebus, a stage similar to the Charon boss fight.
In Phase I and Phase III , the Player needs plenty of room to dodge attacks quickly and precisely.
In Phase II and Phase IV , the Snake needs pools or rivers of Styx to jump into while the Player needs room to dodge the AoE damage attacks, maneuver through the Snake's body, and deal damage to the body.
Phases
Intro Sequence
placeholder pictures
To highlight that both the Echidna and the Snake are actors in the fight, both have at least one line of text at the beginning.
Even if the Snake always goes:
Phase 1
Health
100%
Start
The fight starts with the usual short telegraph while the Player's movement is blocked.
Both actors are highlighted, getting ready to fight with separate animations. The Player needs to notice both the Echidna and the Snake.
The Player's movement returns.
Attacks
Swipe I
Actor
Echidna
The Echidna sends long waves across the level that can be dashed through and blocked by the shield.
Three horizontal thin cone shaped waves from the sides of the level and one extending thin half circle waves attack from the Echidna.
The attack ignores all environmental obstacles.
The Player cannot hide from it behind pillars or water.
The attack cannot be reflected.
The pattern can be
- left, right, left, Echidna
- right, left, right, Echidna
It cannot be interrupted.
During the attack, the Snake is idle and poison spit evaporates before it starts.
After the last swipe, the Echidna is idle for a little while to give the Player a bit of a down-time and the chance to deal damage.
Magic Toss I
Actor
Echidna
The Echidna locks onto the Player and throws multiple magic bombs to their position.
The bombs aren't homing.
They work similar to the Inferno-Bombers single throw attacks but they have clear cross-hair type telegraphing on the floor while they're thrown, like the Fireballs in Asphodel.
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Poison Spit
Actor
Snake
The Snake spits several clouds of a poison gas to random points of the level.
The poison deals damage over time in an area, similar to the Fireballs in Asphodel.
The landing point of the clouds is clearly telegraphed during the throw, like the Fireballs in Asphodel.
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The poison clouds stay in the level for a little while.
Their lifetime is randomized between 5 and 7 seconds. They don't all disappear at the same time (unless they're disrupted by a phase change or swipe attack).
Snake Strike I
Actor
Snake
The telegraphing for this attack is rather long, giving the Player time to notice the rapid strike following it.
The Snake retreats, roars, and prepares to attack.
It strikes from the edge of the level to the Player's position, hitting its head into the ground.
It retreats immediately, not leaving much of a window to strike it during the attack.
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In the short moments the Snake is extended to where the Player was, it can take damage.
The body blocks the way but is dash-able.
The head and body to not deal any damage on stay and retreat, only on the strike.
End
Both actors become invulnerable and retreat to their spawn point.
All remaining attacks stop, poison clouds evaporate.
Phase 2
Health
65%
Start
The Snake takes control of the entire body, the Echidna becomes inactive both as an actor and visually.
Any Level Design changes come into effect now.
The Snake roars, stops being invincible, then leaps into the Erebus / Styx pools in the level, dragging its body behind.
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Attacks
Snake Leaps I
Actor
Snake
The first leap deals damage in a bigger area than the following leaps.
The Snake follows the Player around through the pools or rivers of Styx, as if Zagreus were the food in the classic Snake game.
The Snake's body blocks the way but is dash-able and takes damage.
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At 45% health, the Snake's body starts to emit periodic pulses of damage like spikes or electrical surges.
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End
The Snake becomes invulnerable and retreats to its origin point. It seems tired and frustrated.
The Echidna returns to her origin point.
Any Level Design changes come into effect now.
Phase 3
Health
35%
Start
As the phase changes, the Echidna telegraphs that she is active again with an animation and the occasional voice line.
The voice line happens when the Player is in this boss fight and phase for the first time, all other times are random.
The Snake returns to normal animation, recovered from being tired.
Both actors stop being invincible and start attacks.
Attacks
Summons
Actor
Echidna
The Echidna casts a spell and summons wretches that are known to the Player already.
During the spell, her other actions are blocked.
When the wretches are there, she is free to use other attack again.
The attack does not stack with her Wave attack.
The wretches appear with altered behavior:
- they stay at the edge of the level
- they cannot be damaged
- they attack n amount of times
- they disappear once their attack(s) are over
The Echidna summons one of the following wretch groups at random, per Summons attack:
- Wave Hydra
- Magma Spittle Hydra
- Gorgons
The Wave Hydra sends its usual wave across the level.
The Magma Spittle Support Head spits its usual Fireball on the level.
The Gorgons shoot their usual homing petrifying missiles at the Player.
Swipe II
Actor
Echidna
Magic Toss II
Actor
Echidna
Snake Strike II
Actor
Snake
The telegraphing is a bit shorter so that the pace picks up, in comparison to Snake Strike I.
The Snake strikes to the Player's position, slamming its head into the floor, dealing damage in a large area.
The impact of the strike stuns the Snake.
It remains at the strike position for 2-3 seconds.
During that time, the Snake's body blocks the way but is dash-able and takes damage.
After the stun, the Snake retreats to its origin point and is ready for another attack.
The head and body to not deal any damage on stay and retreat, only on the strike.
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End
Both actors become invulnerable and retreat to their spawn point.
All remaining attacks stop, summons and their attacks disappear immediately.
Phase 4 - Outro
Health
0% (1 hp remains)
Start
Phase IV starts like Phase II with the Snake taking control of the entire body and the Echidna becoming fully inactive.
Any Level Design changes come into effect now.
The Snake emits a quiet and exhausted sound, stops being invincible, then leaps into the Erebus / Styx pools in the level, dragging its body behind.
Attacks
Snake Leaps II
It is much slower and deals less damage.
It travels through the level at random, telegraphing where it will dive next.
It does not deal damage with its body.
One hit defeats the boss.
End
Once the final blow lands, the Echidna boss disappears into the river Styx like all bosses, when they're defeated.
This moment is accompanied by a voice line of the Echidna or sound of the Snake.
Loot
If bounty conditions are met
Other
1 diamond
250 darkness (affected by boons)
Pacing
Beats, Scenes, Sequence
Borrowing theater terms, the fight is divided into parts as follows:
Beats
Scenes
Sequence
individual attacks
phases
boss fight
The sequence consists of four scenes which have different beats each.
Some of the beats can be stacked, changing the difficulty accordingly. The swipe attacks and the leaps block all other attacks from happening. They do not stack.
If an actor is busy, it can't start another attack. The poison spit and summon have a total duration that allows these beats to stack with others from the same actor.
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Diagrams are not true to time scale
Visual Requirements
Echidna
The Echidna is a humanoid being and able to wield magic.
Most important are her telegraphs for when she prepares the Swipe attack, Magic Toss, and summons wretches.
For that, grand gestures that are supported by arms, hands, or hair would work best.
She is a stationary boss, moving only slightly in around her point of origin but without changing the hitbox too much.
Her body is submerged in the River Styx but if that's from down her hips, chest, or any other point does not matter.
She can be rather big and imposing to fit the ancient feel of the Gods and her role as the Hydra's and Cerberus' mother, or closer to Zagreus' size as she will be much longer than him anyway. Her size needs to fit to the Snake's body diameter during the Snake Leaps so those requirements need to be met somehow.
Snake
The Echidna's Snake tail must end in a snake head rather than a tail tip.
It is clearly its own actor, but still part of the Echidna's body and mind, so a design that distinguishes them as actors but brings them together thematically is best.
The Snake uses a lot of strike attacks so it need to extend out of the River Styx and do so quickly.
It uses both ground strike and river dive attacks.
The river dives, it executes with no problem.
The ground strikes stun it when it hits the ground too hard so the head is not fully armor plated to an extend where it would prevent the Snake from being stunned.
During the Snake Leap attacks, the Snake takes control of the body.
It dives through pools or rivers that might be as narrow as its body, meaning the Echidna needs to assume the same width at that point.
Additionally, having the Echidna simply flail around at the end would make it look really silly so another solution needs to be found. The Echidna cannot be rooted at her point of origin as the body forms walls around the level that need to disappear at one point while the body is dragged after the head.
Feedback & Telegraphing
Animation Sequences
Every attack is telegraphed with a short animation from the actor it concerns.
The Player needs to be able to learn each attack's tell to react accordingly.
Requirements are in the attacks' descriptions.
VFX
The visual effects of the Echidna and the Snake need to be easily differentiated to help the Player prioritize and read the battle field as it might get cluttered due to the multiple actors.
It is important that similar effects are used for similar attacks, like Snake Strike I and Snake Strike II, though the difference in damage and area need to be apparent immediately.
Sound
Sound effects are needed to highlight that both the Echidna and the Snake are actors and enemies, at the beginning of the fight.
During the fight, sound effects signalize attacks that are beginning soon, and the impact of each attack.
It is important that similar effects are used for similar attacks, like Snake Strike I and Snake Strike II, though the difference in damage and area need to be apparent immediately.
Rejected
Homing magic missiles
A projectile that's closing in on the Player's position.
Whether it's a wave or a missile, it would be very similar to the Gorgons' move. I opted for the Magic Toss instead as that is a more forgiving attack that feels like it can be used more regularly without being overly frustrating.
Additionally, it makes the summoned Gorgons' move a more unique challenge.
Summons (Slammer Hydra Head, Summoner Hydra Head, Cerberus)
The Summoner Hydra head spits eggs that spawn more enemies.
A summoned wretch that summons more wretches felt wrong and unfair in a fight with multiple fixed actors already. If anything, the Echidna could probably summon Bloodless on her own instead of taking the extra step of summoning a Hydra head that summons Bloodless and then disappears without any other actions, even without taking damage.
The Slammer Hydra head adds a lot of confusion to the fight with rapid strikes to the ground that can span the whole level. I decided against it for readability and reaction speed sake. It is a fast attack that immediately takes responsibility which is good for mixing up the pacing of a fight but hard to balance with two other actors with stacking attacks.
I simply wanted the Cerberus to stay unique to Hades' boss fight.
Having the big dog Zagreus loves so much attack him on the orders of two people is not something I want to do to the Player.
