The Binding of Isaac

Faina Tatarenko + Transistor, Corentin Gaspoz]

Genre	roguelike dungeon crawler, top-down view shooter
Release	September 28, 2011
Developers	Edmund McMillen, Florian Himsl
Game modes	single player, coop
Engine	Adobe Flash
Platforms	Windows, OS X, Linux

Game Overview

The Binding of Isaac is an indie roguelike video game originally released in 2011 using Adobe Flash as its engine. Since 2011, The Binding of Isaac has been updated several times, with the Wrath of the Lamb DLC (May 28, 2012) and the Eternal Update (May 05, 2015). Its 2014 remake, The Binding of Isaac: Rebirth used a custom engine, was expanded with several DLCs, and added more content and gameplay modes.

The story of the game focuses on Isaac, a child who flees into his house’s cellar to escape his religious mother who tries to kill him as proof of her faith.

In the game, the player controls one of the 7 playable characters, Isaac being the main one, and moves through a procedurally generated “dungeon”. Along the way, the player must go through monsters to unlock new rooms, kill bosses to unlock new floors, get rewards for defeating enemies, and explore the level for resources. The game combines linear progression (going down the set amount of floors to reach the bottom of the “dungeon”) with a free roam through a procedurally generated labyrinth of rooms that makes up each of the floors.

The player controls one character and engages in real-time combat against various monsters. All fights are contained within one room. Different rooms have different layouts, including obstacles (rocks, pits), hazards (spikes, fires), and rewards (chests, pickups, items). Additionally, the rooms are divided into types depending on their function (normal room, Shop, Treasure Room, Boss Room, etc).

The Importance of Sound

Sound plays two important roles in The Binding of Isaac. First of all, the game uses sound effects to warn the player of enemy attacks, boss phases, items being activated, and other things they would need to keep an eye on during active combat with many moving elements. Secondly, using ambiance and sound effects, the game sets the mood of various encounters and assists in understanding the narrative progression down the floors of the “dungeon”.

i. Theme

The game doesn’t work on fully immersing the player into the world using any tools—be it visuals, music or sound effects—because the game by its premise is supposed to be influenced heavily by a perception of an impressionable child, it looks and sounds patchworked. Many of the sound effects sound unnatural, over-the-top and mismatched.

Making them so mismatched, however, makes them distinct! By listening to the various unique sound effects alone during combat, the player can distinguish between and keep track of different enemies, projectiles, and their own health, even if their visual attention is limited.

ii. Action + Sound

As the structure of the “dungeon” is built around floors which consist of interconnected rooms, the first and foremost action accompanied by sound is the opening and closing of rooms.

Boss room's door closes

Opening a locked door is also followed by a special sound to let the player know they used up a key.

A door is unlocked

Secret rooms play a special sound upon being discovered to highlight their importance.

Secret room is discovered

Angel/Devils rooms, which only open under specific circumstances after a boss fight, have their own sounds too.

An angel room is opened A devil room is opened

Moving through the room after it's been explored doesn’t make any sounds of their own, so the sound effects here are meant to highlight the progress and exploration of the floor.

To fight, the player uses different projectiles. They all have distinct sounds, including sounds of being shot and getting destroyed/hitting something.

A projectile (tear) is fired A projectile (tear) hits something

Upgrades that change the player’s projectiles also often change the sounds they make. Because the player gets upgrades gradually while moving down the “dungeon”, they get used to the deviations from the default tear sounds one upgrade at a time.

Most of the sounds in TBoI are focused on fighting (having unique sounds for different enemies and projectiles). The addition of sounds of footsteps, wing flaps, or other movement would overwhelm the player; for that reason, player movement is silent.

After defeating all enemies in a room, the player sometimes receives a reward. Different rewards spawn with different sounds, which also helps the player to notice it even if they’re already rushing into the next room.

A chest is spawned/dropped A key is spawned/dropped

The player may use items to assist them during fights, or for utility. Different items have different sound effects, appropriate to the item.

The "Bible" item The "Book of Belial" item The "Scissors" item

Some of them are rechargeable and can be used multiple times as long as the player holds on to them.

A charge is added to the held item An item is charged using a battery

Other items (pickups) are single-use and play a specific sound effect.

The "Moon" card opens the secret room The "Moon" card teleports to the secret room The "Lemon Party" pill spills a puddle of lemonade

Note that different items sometimes play the same sound if they have the same effect: the „Lemon Mishap“ item and „Lemon Party“ pill, the „Book of Belial“ item and the „Devil“ card.

Many interactable items play specific sound(s) for specific situations. For example, the slot machine will play separate sounds for being activated, dropping an item, not dropping anything, and exploding.

A slot machine is activated A slot machine drops an item A slot machine doesn't drop anything A slot machine explodes

iii. Communication with the player

Enemies telegraph their actions using visuals, sounds, or both. Some enemies don’t make any sounds while charging, but do produce a distinct sound effect during their attack.

A Vis enemy shoots a blood laser

Some enemies stay silent even when attacking. Some enemies don’t have special attacks and periodically produce ambient sounds.

Ambient grunt some enemies make Ambient buzzing of a fly

Some enemies, especially bosses, warn the player with sounds before certain attacks.

Mother grunts to warn of her signature attack

The only environment sounds in TBoI are the ambiance of the floor and the sounds of the environment being interacted with (rocks exploding, doors being opened).

Rocks being destroyed

iv. Space

The sounds are always limited to 1 room. The sounds from other rooms don’t pass through the doors, neither open nor closed, which makes it impossible to guess what’s going on in them, while on the other hand doesn’t distract the player from the current room.

The audio is mono instead of stereo, because 1 room always fits 1 screen, and there’s no need to inform the player of any enemies that might be off-screen.

There is no “nature” or “outside” ambiance, as the game always takes place in a “dungeon”. In that sense, the floors and the rooms are self-contained.

v. Dramaturgy/Narration

Within the same floor: the opening of secret or special rooms is marked with special sounds. This helps to mark the progression or achievements that the player might make.

While going down the floors: the ambience changes, as well as the general soundscape. The enemies change as the player moves lower through the floor and, accompanied by the visuals, create a unique “aesthetic” for every floor/zone.

Sountrack of the Caves level Sountrack of the Cathedral level Sountrack of the Chest level

As for the voiceovers, The Binding of Isaac uses pre-recorded lines and soundbytes in various ways:

narration of the intro cutscene;

The intro cutscene

accompany some items;

Bad pill effect

enemy/boss sound effects—voice;

Satan boss appears

enemy/boss sound effects—grunt/scream/distorted or cutoff speech;

Generic monster grunt Mother is hurt

part of ambiance/soundtrack.

The "Cathedral" floor soundtrack

Conclusion & Subjective Thoughts

The sound effects in The Binding of Isaac are at times ridiculous, don’t follow one theme, and clash. However, they fit the setting of the game wonderfully, and accomplish their goal: all the sound effects are unique, recognizable and informative. They help to orient the player during the at times hectic gameplay, and enrich the narrative as well: fleshy, techy, angelic and satanic SFX and ambiances give different areas of the game their own distinct feeling.

Comparison with Transistor

As compared to Transistor in terms of combat, The Binding of Isaac fights are always real-time and for that reason more hectic. The sounds inform the player of what’s happening in the room and serve a more utilitarian function instead of Transistor’s “sound sequence as a reward” that plays at the end of the strategic TURN() mode.

As for the narrative function of sound, The Binding of Isaac and Transistor are similar yet different. Their soundtracks (both music and sound effects) create a unique atmosphere for every “level” or “zone”. However, Transistor has a more defined cyberpunk world/theme, with nature sounds being rare and creating a stark contrast to the majority of the game. On the other hand, The Binding of Isaac mixes the themes more freely, between and within the same level. (While moving within the same floor, the player can enter the Shop, the Secret Room, or the Angel Room, which all sound distinct from each other and have different moods.)

In a sense, Transistor’s soundtrack is more unified and immersive, while The Binding of Isaac’s is patchworked and all over the place.