diff --git a/core/src/NetherGen.cpp b/core/src/NetherGen.cpp
new file mode 100644
index 0000000..498ee3d
--- /dev/null
+++ b/core/src/NetherGen.cpp
@@ -0,0 +1,159 @@
+#include "vf/NetherGen.h"
+
+#include <cmath>
+#include <cstdlib>
+
+namespace vf {
+
+namespace {
+
+uint32_t mixCoord(uint32_t seed, int gx, int gy, int gz) {
+    uint64_t h = 1469598103934665603ull;
+    auto mix = [&h](uint32_t v) {
+        h ^= v;
+        h *= 1099511628211ull;
+    };
+    mix(seed);
+    mix(static_cast<uint32_t>(gx));
+    mix(static_cast<uint32_t>(gy));
+    mix(static_cast<uint32_t>(gz));
+    h ^= h >> 33;
+    return static_cast<uint32_t>(h ^ (h >> 32));
+}
+
+bool replaceable(Block block) {
+    return block == Block::Air || block == Block::Lava;
+}
+
+} // namespace
+
+NetherGenerator::NetherGenerator() : NetherGenerator(Params{}) {}
+
+NetherGenerator::NetherGenerator(const Params& netherParams)
+    : params(netherParams),
+      floorNoise(netherParams.seed ^ 0x4e455448u),
+      ceilingNoise(netherParams.seed ^ 0x524f4f46u),
+      caveNoise(netherParams.seed ^ 0x43415645u),
+      blobNoise(netherParams.seed ^ 0x424c4f42u),
+      oreNoise(netherParams.seed ^ 0x5155415au),
+      biomeNoise(netherParams.seed ^ 0x42494f4du) {}
+
+NetherBiome NetherGenerator::biomeAt(int gx, int gz) const {
+    float f = params.biomeFrequency;
+    float heat = biomeNoise.simplex2D(gx * f, gz * f);
+    float damp = biomeNoise.simplex2D(gx * f * 1.7f + 91.3f, gz * f * 1.7f - 44.7f);
+
+    if (damp < -0.30f) return NetherBiome::SoulSandValley;
+    if (heat > 0.34f) return NetherBiome::BasaltDeltas;
+    if (damp > 0.26f) return NetherBiome::CrimsonForest;
+    return NetherBiome::NetherWastes;
+}
+
+NetherColumn NetherGenerator::columnAt(int gx, int gz) const {
+    NetherColumn column;
+    column.biome = biomeAt(gx, gz);
+    column.lavaLevel = params.lavaLevel;
+
+    float ff = params.floorFrequency;
+    float broad = floorNoise.fbm2D(gx * ff, gz * ff, 4, 2.0f, 0.5f);
+    float rough = floorNoise.noise2D(gx * ff * 3.1f + 17.0f, gz * ff * 3.1f - 9.0f);
+
+    int floorCentre = params.lavaLevel + 3;
+    float amplitude = 12.0f;
+    switch (column.biome) {
+        case NetherBiome::SoulSandValley:
+            floorCentre -= 8;
+            amplitude = 15.0f;
+            break;
+        case NetherBiome::BasaltDeltas:
+            floorCentre -= 3;
+            amplitude = 9.0f;
+            break;
+        case NetherBiome::CrimsonForest:
+            floorCentre += 4;
+            amplitude = 8.0f;
+            break;
+        default:
+            break;
+    }
+
+    float shaped = broad * 0.78f + rough * 0.22f;
+    column.floorHeight = floorCentre + static_cast<int>(std::lround(shaped * amplitude));
+
+    float cf = params.ceilingFrequency;
+    float roof = ceilingNoise.fbm2D(gx * cf, gz * cf, 3, 2.0f, 0.5f);
+    column.ceilingHeight = params.ceilingY - params.roofThickness +
+                           static_cast<int>(std::lround(roof * 7.0f));
+
+    int lowest = params.floorY + params.bedrockThickness + 1;
+    int highest = params.ceilingY - params.bedrockThickness - 2;
+    if (column.floorHeight < lowest) column.floorHeight = lowest;
+    if (column.floorHeight > highest - 12) column.floorHeight = highest - 12;
+    if (column.ceilingHeight > highest) column.ceilingHeight = highest;
+    if (column.ceilingHeight < column.floorHeight + 10) column.ceilingHeight = column.floorHeight + 10;
+
+    column.drowned = column.floorHeight < params.lavaLevel;
+    return column;
+}
+
+bool NetherGenerator::isCarved(int gx, int gy, int gz) const {
+    float f = params.caveFrequency;
+    float first = 1.0f - std::fabs(caveNoise.noise3D(gx * f, gy * f * 1.9f, gz * f));
+    float second = 1.0f - std::fabs(caveNoise.noise3D(gx * f + 41.3f, gy * f * 1.9f - 17.9f,
+                                                      gz * f + 23.1f));
+    return first > params.caveThreshold && second > params.caveThreshold;
+}
+
+bool NetherGenerator::isBlob(int gx, int gy, int gz) const {
+    float broad = blobNoise.noise3D(gx * 0.026f, gy * 0.019f, gz * 0.026f);
+    float detail = blobNoise.noise3D(gx * 0.056f + 7.3f, gy * 0.048f - 3.1f, gz * 0.056f + 2.7f);
+    return broad + detail * 0.42f > params.blobThreshold;
+}
+
+bool NetherGenerator::isBedrock(int gx, int gy, int gz) const {
+    if (gy == params.floorY || gy == params.ceilingY - 1) return true;
+
+    int fromFloor = gy - params.floorY;
+    int fromCeiling = params.ceilingY - 1 - gy;
+    int band = -1;
+    if (fromFloor > 0 && fromFloor < params.bedrockThickness) band = fromFloor;
+    else if (fromCeiling > 0 && fromCeiling < params.bedrockThickness) band = fromCeiling;
+    if (band < 0) return false;
+
+    uint32_t roll = mixCoord(params.seed ^ 0x42454452u, gx, gy, gz);
+    return static_cast<int>(roll % static_cast<uint32_t>(params.bedrockThickness)) >= band;
+}
+
+Block NetherGenerator::topFor(NetherBiome biome) const {
+    switch (biome) {
+        case NetherBiome::SoulSandValley: return Block::SoulSand;
+        case NetherBiome::BasaltDeltas: return Block::Basalt;
+        case NetherBiome::CrimsonForest: return Block::Moss;
+        default: return Block::Netherrack;
+    }
+}
+
+Block NetherGenerator::fillerFor(NetherBiome biome) const {
+    switch (biome) {
+        case NetherBiome::SoulSandValley: return Block::SoulSoil;
+        case NetherBiome::BasaltDeltas: return Block::Blackstone;
+        default: return Block::Netherrack;
+    }
+}
+
+Block NetherGenerator::blockAt(const NetherColumn& column, int gx, int gy, int gz) const {
+    if (gy < params.floorY || gy >= params.ceilingY) return Block::Air;
+    if (isBedrock(gx, gy, gz)) return Block::Bedrock;
+
+    bool inMass = gy <= column.floorHeight || gy >= column.ceilingHeight;
+    bool solid = inMass || isBlob(gx, gy, gz);
+    if (solid && isCarved(gx, gy, gz)) solid = false;
+    if (!solid) return gy <= params.lavaLevel ? Block::Lava : Block::Air;
+
+    Block material = Block::Netherrack;
+    if (gy <= column.floorHeight) {
+        int depth = column.floorHeight - gy;
+        if (depth == 0) material = topFor(column.biome);
+        else if (depth <= 3) material = fillerFor(column.biome);
+    }
+