Level Design Patterns

Spatial content design patterns for Nethercore ZX games. Covers tile-based 2D layouts, 3D level flow, procedural generation, and pacing—all within ZX ROM constraints.

Level Type Overview

Level Type	Perspective	Storage	Generation
Tile Map	2D/Top-Down	Grid arrays	Hand-crafted or procedural
Room-Based	Any	Room + connection data	BSP, graph-based
Open World	3D	Chunked sectors	Streaming, LOD
Linear	Any	Sequential segments	Hand-crafted

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Tile-Based Design (2D)

Grid-based levels using tile indices. Efficient storage and collision.

Tile Map Structure

const TILE_SIZE: u32 = 16;
const MAP_WIDTH: usize = 64;
const MAP_HEIGHT: usize = 48;

struct TileMap {
    tiles: [u8; MAP_WIDTH * MAP_HEIGHT],  // Tile indices
    collision: [u8; MAP_WIDTH * MAP_HEIGHT],  // Collision flags
}

impl TileMap {
    fn get_tile(&self, x: usize, y: usize) -> u8 {
        if x < MAP_WIDTH && y < MAP_HEIGHT {
            self.tiles[y * MAP_WIDTH + x]
        } else {
            0  // Out of bounds = empty
        }
    }

    fn is_solid(&self, x: usize, y: usize) -> bool {
        if x < MAP_WIDTH && y < MAP_HEIGHT {
            self.collision[y * MAP_WIDTH + x] != 0
        } else {
            true  // Out of bounds = solid
        }
    }

    fn world_to_tile(&self, world_x: f32, world_y: f32) -> (usize, usize) {
        ((world_x / TILE_SIZE as f32) as usize,
         (world_y / TILE_SIZE as f32) as usize)
    }
}

Collision Layers

Use bitflags for multi-layer collision:

const COLLISION_NONE: u8 = 0b0000_0000;
const COLLISION_SOLID: u8 = 0b0000_0001;
const COLLISION_PLATFORM: u8 = 0b0000_0010;  // One-way
const COLLISION_HAZARD: u8 = 0b0000_0100;
const COLLISION_WATER: u8 = 0b0000_1000;
const COLLISION_LADDER: u8 = 0b0001_0000;

fn check_collision(flags: u8, mask: u8) -> bool {
    (flags & mask) != 0
}

Tile Types (Platformer)

Category	Tiles	Purpose
Terrain	Ground, walls, slopes	Core geometry
Platforms	Solid, one-way, moving	Traversal
Hazards	Spikes, lava, pits	Obstacles
Interactables	Doors, switches, chests	Progression
Decorative	Background, foreground	Visual only

See references/tile-map-patterns.md for chunk streaming and large map handling.

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3D Level Layout

Spatial flow principles for third-person and first-person games.

Layout Principles

Landmarks: Place distinct visual features for orientation. Players navigate by memorable geometry, not minimaps.

Sight Lines: Control what players see. Long sight lines build anticipation; blocked views create surprise.

Verticality: Use height changes for:

• Pacing variation (climb = slow, drop = fast)
• Combat advantage (high ground)
• Exploration reward (hidden areas above/below)

Flow Loops: Design levels as interconnected loops, not dead-ends. Players should return to familiar areas with new access.

Critical Path vs Exploration

Level Structure:
├── Critical Path (required)
│   ├── Clear signposting
│   ├── Moderate challenge
│   └── Story beats
└── Optional Areas (reward exploration)
    ├── Collectibles
    ├── Shortcuts
    └── Harder challenges

Space Budgeting

Area Type	Size (units)	Purpose
Combat Arena	30×30 minimum	Room to maneuver
Corridor	4-6 wide	Transition, tension
Hub Room	50×50+	Orientation, choices
Boss Arena	60×60+	Epic encounters

---

Procedural Generation

Deterministic algorithms for rollback-safe level creation.

Room-Based Generation (BSP)

Binary Space Partitioning creates dungeon-like layouts:

struct Room {
    x: u16, y: u16,
    width: u16, height: u16,
}

struct Dungeon {
    rooms: Vec<Room>,
    corridors: Vec<(usize, usize)>,  // Room index pairs
}

fn generate_dungeon(seed: u32, width: u16, height: u16,
                    min_room: u16, max_room: u16) -> Dungeon {
    // Seed the deterministic RNG
    seed_random(seed);

    let mut rooms = Vec::new();
    let mut areas = vec![(0u16, 0u16, width, height)];

    // Recursively split areas
    while let Some((x, y, w, h)) = areas.pop() {
        if w < min_room * 2 || h < min_room * 2 {
            // Area too small to split, create room
            let room_w = random_range(min_room as i32, w.min(max_room) as i32) as u16;
            let room_h = random_range(min_room as i32, h.min(max_room) as i32) as u16;
            let room_x = x + random_range(0, (w - room_w) as i32) as u16;
            let room_y = y + random_range(0, (h - room_h) as i32) as u16;
            rooms.push(Room { x: room_x, y: room_y, width: room_w, height: room_h });
        } else {
            // Split horizontally or vertically
            if random() % 2 == 0 && w > min_room * 2 {
                let split = random_range(min_room as i32, (w - min_room) as i32) as u16;
                areas.push((x, y, split, h));
                areas.push((x + split, y, w - split, h));
            } else if h > min_room * 2 {
                let split = random_range(min_room as i32, (h - min_room) as i32) as u16;
                areas.push((x, y, w, split));
                areas.push((x, y + split, w, h - split));
            }
        }
    }

    // Connect adjacent rooms with corridors
    let corridors = connect_rooms(&rooms);

    Dungeon { rooms, corridors }
}

Determinism Requirements

All procedural generation MUST use ZX FFI random functions:

Use	Correct	Incorrect
Seed	seed_random(seed)	srand(), system time
Values	random(), random_range()	rand(), external RNG

Same seed = identical level across all clients (rollback-safe).

See references/procedural-generation.md for noise-based terrain and room templates.

---

Pacing and Difficulty

Control player experience through intentional rhythm.

Difficulty Curve Patterns

Pattern	Shape	Use Case
Linear	/	Tutorial → mastery
Sawtooth	/\/\/\	Tension/release cycles
Plateau	_/‾‾‾	Skill gates then mastery zone
Inverse	\	Power fantasy, late-game ease

Intensity Graph

Map sections by intensity (0-10):

Level Flow:
Start [2] → Combat [6] → Puzzle [3] → Miniboss [8] → Rest [2] → Boss [10]

Visualized:
10 |                                              ████
 8 |              ████                            ████
 6 |    ████      ████                            ████
 4 |    ████      ████      ████                  ████
 2 | ████████     ████      ████████    ████████  ████
   └──────────────────────────────────────────────────
     Start    Combat   Puzzle   Mini   Rest    Boss

Checkpoint Placement

• Every 30-60 seconds of gameplay
• Before difficulty spikes (not after)
• After learning new mechanics
• Never mid-combat or mid-puzzle

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ZX Constraints

ROM budget considerations for level data.

Storage Estimates

Data Type	Size	Notes
Tile index	1 byte	256 tile types
64×48 map	3 KB	Single screen
256×256 map	64 KB	Large area
Room template	200-500 bytes	Procedural building block
Collision layer	Same as tile layer	Can compress with RLE

Streaming Strategy

For large worlds, stream chunks:

const CHUNK_SIZE: usize = 32;  // 32×32 tiles per chunk
const LOADED_RADIUS: usize = 2;  // Load chunks within 2 of player

struct WorldStreamer {
    loaded_chunks: HashMap<(i32, i32), Chunk>,
    player_chunk: (i32, i32),
}

fn update_streaming(streamer: &mut WorldStreamer, player_x: f32, player_y: f32) {
    let new_chunk = (
        (player_x / (CHUNK_SIZE * TILE_SIZE) as f32) as i32,
        (player_y / (CHUNK_SIZE * TILE_SIZE) as f32) as i32,
    );

    if new_chunk != streamer.player_chunk {
        // Unload distant chunks, load nearby chunks
        // Keep within ROM streaming budget
    }
}

Compression Tips

• Use RLE for repetitive tile runs
• Store room templates, instantiate at runtime
• Procedural generation trades CPU for storage

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Additional Resources

Reference Files

• references/tile-map-patterns.md — Complete tile systems, chunk loading, editor integration
• references/procedural-generation.md — BSP, cellular automata, wave function collapse basics

Related Skills

• gameplay-mechanics — Player movement and interaction patterns
• physics-collision — Collision detection for level geometry

Conceptual Design

For flow, pacing, and challenge curves (without code): use game-design:level-design.