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2026-04-10 22:59:39 +08:00
commit cc2e7b9bb0
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+/**
+ * Explosion.js
+ * Simple explosion effect using frame-based animation.
+ * Managed via object pool for performance.
+ */
+
+class Explosion {
+  constructor() {
+    this.x = 0;
+    this.y = 0;
+    this.alive = false;
+    this.size = 0;
+    this.maxSize = 30;
+    this._timer = 0;
+    this._duration = 0.3; // seconds
+    this._phase = 0; // 0 to 1
+    this._isBig = false; // big explosion for tank destruction
+  }
+
+  /**
+   * Initialize the explosion.
+   * @param {number} x - Center X.
+   * @param {number} y - Center Y.
+   * @param {boolean} [isBig=false] - Whether this is a large explosion (tank death).
+   */
+  init(x, y, isBig = false) {
+    this.x = x;
+    this.y = y;
+    this.alive = true;
+    this._timer = 0;
+    this._phase = 0;
+    this._isBig = isBig;
+    this.maxSize = isBig ? 50 : 25;
+    this._duration = isBig ? 0.5 : 0.3;
+  }
+
+  /**
+   * Update explosion animation.
+   * @param {number} dt - Delta time in seconds.
+   */
+  update(dt) {
+    if (!this.alive) return;
+
+    this._timer += dt;
+    this._phase = this._timer / this._duration;
+
+    if (this._phase >= 1) {
+      this.alive = false;
+      return;
+    }
+
+    // Size grows then shrinks
+    if (this._phase < 0.4) {
+      this.size = this.maxSize * (this._phase / 0.4);
+    } else {
+      this.size = this.maxSize * (1 - (this._phase - 0.4) / 0.6);
+    }
+  }
+
+  /**
+   * Render the explosion.
+   * @param {CanvasRenderingContext2D} ctx
+   */
+  render(ctx) {
+    if (!this.alive) return;
+
+    ctx.save();
+
+    const alpha = 1 - this._phase * 0.5;
+    ctx.globalAlpha = alpha;
+
+    // Outer glow
+    if (this._isBig) {
+      ctx.fillStyle = '#FF4500';
+      ctx.beginPath();
+      ctx.arc(this.x, this.y, this.size * 1.2, 0, Math.PI * 2);
+      ctx.fill();
+    }
+
+    // Main explosion
+    ctx.fillStyle = '#FF8C00';
+    ctx.beginPath();
+    ctx.arc(this.x, this.y, this.size, 0, Math.PI * 2);
+    ctx.fill();
+
+    // Inner bright core
+    ctx.fillStyle = '#FFFF00';
+    ctx.beginPath();
+    ctx.arc(this.x, this.y, this.size * 0.5, 0, Math.PI * 2);
+    ctx.fill();
+
+    // White center flash (early phase only)
+    if (this._phase < 0.3) {
+      ctx.fillStyle = '#FFFFFF';
+      ctx.beginPath();
+      ctx.arc(this.x, this.y, this.size * 0.2, 0, Math.PI * 2);
+      ctx.fill();
+    }
+
+    ctx.restore();
+  }
+}
+
+module.exports = Explosion;