логика выделена в отдельный набор классов

src/game/entities/ResourceDrop.ts

@@ -0,0 +1,100 @@
+import { makeAutoObservable } from 'mobx';
+import {
+  DROP_COLLECT_ARC_HEIGHT,
+  DROP_COLLECT_DURATION,
+  DROP_EJECT_RADIUS,
+  DROP_FALL_ARC_HEIGHT,
+  DROP_FALL_DURATION,
+} from '../constants';
+import { randomId } from '../id';
+import type { DropPhase, Flight, ResourceDropData, ResourceType, Vec2 } from '../types';
+
+/** A resource in flight — ejected from a chopped node or a killed rabbit, falling to a landing
+ * spot, then (once the character gets close) flying into the inventory. Framework-free — no
+ * React/DOM dependency. */
+export class ResourceDrop {
+  readonly id: string;
+  resource: ResourceType;
+  x: number;
+  y: number;
+  /** Visual height above ground during a flight, for the ballistic arc. 0 once landed. */
+  z: number;
+  phase: DropPhase;
+  flight?: Flight;
+
+  constructor(resource: ResourceType, x: number, y: number, z: number, phase: DropPhase, flight: Flight | undefined, id = randomId('drop')) {
+    this.id = id;
+    this.resource = resource;
+    this.x = x;
+    this.y = y;
+    this.z = z;
+    this.phase = phase;
+    this.flight = flight;
+    makeAutoObservable(this, {}, { autoBind: true });
+  }
+
+  /** Ejects a resource from `origin` on a ballistic arc to a random spot within a circle around
+   * it; it only becomes pickable once it lands (see updateFlight). */
+  static eject(origin: Vec2, resource: ResourceType): ResourceDrop {
+    const angle = Math.random() * Math.PI * 2;
+    const landDistance = Math.random() * DROP_EJECT_RADIUS;
+    const toX = origin.x + Math.cos(angle) * landDistance;
+    const toY = origin.y + Math.sin(angle) * landDistance;
+    return new ResourceDrop(resource, origin.x, origin.y, 0, 'falling', {
+      fromX: origin.x,
+      fromY: origin.y,
+      toX,
+      toY,
+      elapsed: 0,
+      duration: DROP_FALL_DURATION,
+      arcHeight: DROP_FALL_ARC_HEIGHT,
+    });
+  }
+
+  /** Reconstructs a drop from saved data (a straight deep copy). */
+  static restore(data: ResourceDropData): ResourceDrop {
+    return new ResourceDrop(data.resource, data.x, data.y, data.z, data.phase, data.flight ? { ...data.flight } : undefined, data.id);
+  }
+
+  /** Starts a landed drop flying into the inventory once the character gets close enough. */
+  startCollecting(target: Vec2): void {
+    this.phase = 'collecting';
+    this.flight = {
+      fromX: this.x,
+      fromY: this.y,
+      toX: target.x,
+      toY: target.y,
+      elapsed: 0,
+      duration: DROP_COLLECT_DURATION,
+      arcHeight: DROP_COLLECT_ARC_HEIGHT,
+    };
+  }
+
+  /** Advances an in-progress flight along its ballistic arc. Returns 'flying' while still en
+   * route, 'landed' the instant a falling flight completes (or if there's no flight at all), or
+   * 'collected' the instant a collecting flight reaches the character — the caller applies the
+   * inventory gain and removes the drop only on 'collected'. */
+  updateFlight(deltaTime: number): 'flying' | 'landed' | 'collected' {
+    if (this.phase === 'landed' || !this.flight)
+      return 'landed';
+
+    const flight = this.flight;
+    flight.elapsed += deltaTime;
+    const t = Math.min(1, flight.elapsed / flight.duration);
+    this.x = flight.fromX + (flight.toX - flight.fromX) * t;
+    this.y = flight.fromY + (flight.toY - flight.fromY) * t;
+    this.z = flight.arcHeight * 4 * t * (1 - t);
+
+    if (t < 1)
+      return 'flying';
+
+    if (this.phase === 'falling') {
+      this.phase = 'landed';
+      this.flight = undefined;
+      this.z = 0;
+      return 'landed';
+    }
+
+    return 'collected';
+  }
+}