Destructible Terrain
Worms' secret weapon
The technique of modifying bitmap landscapes in real-time, famously used in Worms to create satisfying explosions that reshape the battlefield.
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 FunctionThe 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.