Destructible Terrain

Overview

Destructible terrain is a technique where the game landscape is stored as a bitmap or voxel grid that can be modified in real-time — explosions carve holes, weapons reshape ground, the battlefield evolves through play. Popularised by Lemmings (DMA Design, 1991) and perfected by Worms (Team17, 1995), the technique creates satisfying visual feedback and emergent gameplay where the environment becomes part of the strategy.

The roots go back further than the 1990s: Tank (Atari arcade, 1974) had basic terrain destruction; Artillery Duel (1983, ColecoVision) and Scorched Earth (Wendell Hicken, 1991, DOS shareware) established the artillery-game pattern that Worms refined.

Fast facts

Famous use: Worms (Team17, 1995); core mechanic of the entire series.
Direct ancestor: Scorched Earth (1991) — the artillery shareware classic.
Earliest example: Tank (1974, arcade).
Method: Bitmap pixel manipulation + collision detection by colour reading.
Appeal: Satisfying visual and tactile feedback.
Implementation: Circle-fill operations on a backed-up landscape bitmap.

How it works

The classic 2D bitmap approach:

Step	Action
1	Store terrain as a single-colour bitmap (or multi-colour with one "transparent" colour for sky)
2	Detect explosion location and radius
3	Draw a filled circle in "sky/transparent" colour at that location
4	Update collision data (often the bitmap is the collision data)
5	Redraw the affected screen area

Collision detection is then "read the pixel at this position; is it sky or terrain?" — extremely simple and fast.

The Worms implementation

Andy Davidson's approach for Worms (Team17, 1995):

Component	Implementation
Terrain storage	Single bitmap representing the entire battlefield
Explosions	Filled circles drawn in "transparent" sky colour
Collision detection	Read pixel colours at worm position
Falling	Worms fall through new holes naturally — same logic that handles existing terrain
Water	Rises from the bottom; fills lowest areas
Particles	Soil particles spawn at explosion edges, fly outward, settle

The approach was so simple it shipped on the Amiga in 1995, with the same core algorithm ported to every platform since (PC, PSX, GBA, modern PC, mobile). Worms games still ship with this fundamental technique 30 years later.

Why it's satisfying

Element	Effect
Visual feedback	Watch the damage happen in real time
Emergent gameplay	Create new paths, isolate enemies, expose hidden routes
Strategy	The terrain is a resource — controlling it matters
Variety	No two matches play the same; the map evolves through the game
Player expression	"I dug a tunnel through the mountain" is a memorable story

Technical requirements

Component	Need
Bitmap graphics mode	Pixel-level read/write access
Fast fill routines	Circle-fill must be cheap; on Amiga the Blitter handled this
Collision detection	Pixel-colour-based
Efficient redraw	Only redraw changed regions
Memory	Full-resolution backup of the original terrain

Blitz Basic implementation

Worms was famously written in Blitz Basic 2 on the Amiga. A simplified version of the destructible terrain operation:

' Blitz Basic 2 pseudo-code
' Draw a 30-pixel radius hole at (x, y) in sky colour
Color SkyColour
Circle x, y, 30, 1   ' fill mode

' Collision check at worm's foot position
Function IsTerrain(x, y)
   c = Point(x, y)
   IsTerrain = (c <> SkyColour)
End Function

The Blitter's hardware circle-fill made this essentially free on the Amiga. PC ports used software circle-fill that was still fast enough on 1995 hardware.

Earlier examples

Game	Year	Approach
Tank	1974	Arcade — basic destructible barriers
Artillery Duel	1983	ColecoVision — bitmap-based artillery game
Scorched Earth	1991	DOS shareware artillery — direct ancestor of Worms; tank artillery, destructible mountains, dozens of weapons
Lemmings	1991	DMA Design — diggers, bashers, climbers all interacted with the terrain bitmap
Tetris-style with terrain	Various	Vertical terrain destruction in falling-block games
Worms	1995	Perfected the artillery formula
Worms 2	1997	More weapons, animation; same core terrain
Cortex Command	2012	Voxel-based; per-pixel destruction with physics
Noita	2020	Per-pixel falling-everything simulation; every pixel is its own physics object

Modern variants

The technique evolved into several distinct modern forms:

Style	Examples
2D bitmap	Worms series — original and still going
Voxel	Minecraft, Cortex Command, Cube World
Procedural mesh	Red Faction series, Crackdown — fully 3D destructible buildings
Particle-based	Noita — every pixel is an individual particle with physics
Tile-based with destruction	Terraria, Starbound — tile world that responds to mining
Scripted destruction	Most modern shooters — pre-authored damage states rather than free-form

Design implications

Destructible terrain creates:

Tactical positioning matters — high ground can be denied
Defensive play viable — bunkering becomes strategy
Comeback mechanics — late-game terrain can favour the underdog
Match evolution — early game looks different from late game
Player creativity — building, tunnelling, isolating, walling-in

Legacy

Destructible terrain became a genre staple — from artillery games (Worms, Scorched 3D) to platformers (Terraria, Starbound) to modern shooters (Battlefield: Bad Company 2's tower demolition, Red Faction: Guerrilla's building destruction) to crafting/survival (Minecraft's mining). The technique proved that simple bitmap operations could create deep, emergent gameplay that kept players engaged through unpredictability.

Worms' secret weapon