diff --git a/src/runtime-three/runtime-interaction-system.ts b/src/runtime-three/runtime-interaction-system.ts
new file mode 100644
index 00000000..cd9d157f
--- /dev/null
+++ b/src/runtime-three/runtime-interaction-system.ts
@@ -0,0 +1,218 @@
+import type { Vec3 } from "../core/vector";
+import type { InteractionLink } from "../interactions/interaction-links";
+
+import type { RuntimeInteractable, RuntimeSceneDefinition, RuntimeTeleportTarget, RuntimeTriggerVolume } from "./runtime-scene-build";
+
+const DEFAULT_INTERACTABLE_TARGET_RADIUS = 0.75;
+
+export interface RuntimeInteractionDispatcher {
+  teleportPlayer(target: RuntimeTeleportTarget, link: InteractionLink): void;
+  toggleBrushVisibility(brushId: string, visible: boolean | undefined, link: InteractionLink): void;
+}
+
+export interface RuntimeInteractionPrompt {
+  sourceEntityId: string;
+  prompt: string;
+  distance: number;
+  range: number;
+}
+
+function subtractVec3(left: Vec3, right: Vec3): Vec3 {
+  return {
+    x: left.x - right.x,
+    y: left.y - right.y,
+    z: left.z - right.z
+  };
+}
+
+function scaleVec3(vector: Vec3, scalar: number): Vec3 {
+  return {
+    x: vector.x * scalar,
+    y: vector.y * scalar,
+    z: vector.z * scalar
+  };
+}
+
+function dotVec3(left: Vec3, right: Vec3): number {
+  return left.x * right.x + left.y * right.y + left.z * right.z;
+}
+
+function lengthSquaredVec3(vector: Vec3): number {
+  return dotVec3(vector, vector);
+}
+
+function distanceBetweenVec3(left: Vec3, right: Vec3): number {
+  return Math.sqrt(lengthSquaredVec3(subtractVec3(left, right)));
+}
+
+function normalizeVec3(vector: Vec3): Vec3 | null {
+  const lengthSquared = lengthSquaredVec3(vector);
+
+  if (lengthSquared <= Number.EPSILON) {
+    return null;
+  }
+
+  return scaleVec3(vector, 1 / Math.sqrt(lengthSquared));
+}
+
+function isPointInsideTriggerVolume(position: Vec3, triggerVolume: RuntimeTriggerVolume): boolean {
+  const halfSize = {
+    x: triggerVolume.size.x * 0.5,
+    y: triggerVolume.size.y * 0.5,
+    z: triggerVolume.size.z * 0.5
+  };
+
+  return (
+    position.x >= triggerVolume.position.x - halfSize.x &&
+    position.x <= triggerVolume.position.x + halfSize.x &&
+    position.y >= triggerVolume.position.y - halfSize.y &&
+    position.y <= triggerVolume.position.y + halfSize.y &&
+    position.z >= triggerVolume.position.z - halfSize.z &&
+    position.z <= triggerVolume.position.z + halfSize.z
+  );
+}
+
+function raySphereHitDistance(origin: Vec3, direction: Vec3, center: Vec3, radius: number): number | null {
+  const offset = subtractVec3(origin, center);
+  const halfB = dotVec3(offset, direction);
+  const c = dotVec3(offset, offset) - radius * radius;
+  const discriminant = halfB * halfB - c;
+
+  if (discriminant < 0) {
+    return null;
+  }
+
+  const discriminantRoot = Math.sqrt(discriminant);
+  const nearestHit = -halfB - discriminantRoot;
+
+  if (nearestHit >= 0) {
+    return nearestHit;
+  }
+
+  const farHit = -halfB + discriminantRoot;
+  return farHit >= 0 ? 0 : null;
+}
+
+function resolveTeleportTarget(runtimeScene: RuntimeSceneDefinition, entityId: string): RuntimeTeleportTarget | null {
+  return runtimeScene.entities.teleportTargets.find((teleportTarget) => teleportTarget.entityId === entityId) ?? null;
+}
+
+function hasTriggerLinks(runtimeScene: RuntimeSceneDefinition, sourceEntityId: string, trigger: InteractionLink["trigger"]): boolean {
+  return runtimeScene.interactionLinks.some((link) => link.sourceEntityId === sourceEntityId && link.trigger === trigger);
+}
+
+function getInteractableTargetRadius(interactable: RuntimeInteractable): number {
+  return Math.min(DEFAULT_INTERACTABLE_TARGET_RADIUS, interactable.radius);
+}
+
+export class RuntimeInteractionSystem {
+  private readonly occupiedTriggerVolumes = new Set<string>();
+
+  reset() {
+    this.occupiedTriggerVolumes.clear();
+  }
+
+  updatePlayerPosition(feetPosition: Vec3, runtimeScene: RuntimeSceneDefinition, dispatcher: RuntimeInteractionDispatcher) {
+    for (const triggerVolume of runtimeScene.entities.triggerVolumes) {
+      const containsPlayer = isPointInsideTriggerVolume(feetPosition, triggerVolume);
+      const wasOccupied = this.occupiedTriggerVolumes.has(triggerVolume.entityId);
+
+      if (!wasOccupied && containsPlayer && triggerVolume.triggerOnEnter) {
+        this.dispatchLinks(triggerVolume.entityId, "enter", runtimeScene, dispatcher);
+      } else if (wasOccupied && !containsPlayer && triggerVolume.triggerOnExit) {
+        this.dispatchLinks(triggerVolume.entityId, "exit", runtimeScene, dispatcher);
+      }
+
+      if (containsPlayer) {
+        this.occupiedTriggerVolumes.add(triggerVolume.entityId);
+      } else {
+        this.occupiedTriggerVolumes.delete(triggerVolume.entityId);
+      }
+    }
+  }
+
+  resolveClickInteractionPrompt(viewOrigin: Vec3, viewDirection: Vec3, runtimeScene: RuntimeSceneDefinition): RuntimeInteractionPrompt | null {
+    const normalizedViewDirection = normalizeVec3(viewDirection);
+
+    if (normalizedViewDirection === null) {
+      return null;
+    }
+
+    let bestPrompt: RuntimeInteractionPrompt | null = null;
+    let bestHitDistance = Number.POSITIVE_INFINITY;
+
+    for (const interactable of runtimeScene.entities.interactables) {
+      if (!interactable.enabled || !hasTriggerLinks(runtimeScene, interactable.entityId, "click")) {
+        continue;
+      }
+
+      const distance = distanceBetweenVec3(viewOrigin, interactable.position);
+
+      if (distance > interactable.radius) {
+        continue;
+      }
+
+      const hitDistance = raySphereHitDistance(
+        viewOrigin,
+        normalizedViewDirection,
+        interactable.position,
+        getInteractableTargetRadius(interactable)
+      );
+
+      if (hitDistance === null) {
+        continue;
+      }
+
+      const nextPrompt: RuntimeInteractionPrompt = {
+        sourceEntityId: interactable.entityId,
+        prompt: interactable.prompt,
+        distance,
+        range: interactable.radius
+      };
+
+      if (
+        hitDistance < bestHitDistance ||
+        (hitDistance === bestHitDistance &&
+          (bestPrompt === null ||
+            distance < bestPrompt.distance ||
+            (distance === bestPrompt.distance && interactable.entityId.localeCompare(bestPrompt.sourceEntityId) < 0)))
+      ) {
+        bestHitDistance = hitDistance;
+        bestPrompt = nextPrompt;
+      }
+    }
+
+    return bestPrompt;
+  }
+
+  dispatchClickInteraction(sourceEntityId: string, runtimeScene: RuntimeSceneDefinition, dispatcher: RuntimeInteractionDispatcher) {
+    this.dispatchLinks(sourceEntityId, "click", runtimeScene, dispatcher);
+  }
+
+  private dispatchLinks(
+    sourceEntityId: string,
+    trigger: InteractionLink["trigger"],
+    runtimeScene: RuntimeSceneDefinition,
+    dispatcher: RuntimeInteractionDispatcher
+  ) {
+    for (const link of runtimeScene.interactionLinks) {
+      if (link.sourceEntityId !== sourceEntityId || link.trigger !== trigger) {
+        continue;
+      }
+
+      switch (link.action.type) {
+        case "teleportPlayer": {
+          const teleportTarget = resolveTeleportTarget(runtimeScene, link.action.targetEntityId);
+
+          if (teleportTarget !== null) {
+            dispatcher.teleportPlayer(teleportTarget, link);
+          }
+          break;
+        }
+        case "toggleVisibility":
+          dispatcher.toggleBrushVisibility(link.action.targetBrushId, link.action.visible, link);
+          break;
+      }
+    }
+  }
+}