从零开发游戏需要学习的c#模块，第三十一章（技能冷却系统 —— 范围爆炸）
本节课目标
按鼠标右键释放范围爆炸
爆炸有冷却时间（5秒）
屏幕显示冷却进度图标
爆炸范围内所有敌人受到大量伤害
爆炸有视觉特效
第一步：给 Player 类加技能
打开Player.cs，添加以下内容：
1. 添加字段：
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// 技能系统 private float skillCooldown = 5f; private float skillTimer = 0f; private bool skillReady = true;
2. 添加方法：
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// 尝试释放技能，返回是否成功 public bool TryUseSkill(float deltaTime) { if (!skillReady) { skillTimer -= deltaTime; if (skillTimer <= 0) { skillReady = true; skillTimer = 0; } return false; } return true; } public void UseSkill() { skillReady = false; skillTimer = skillCooldown; } // 技能冷却百分比（0 到 1，0=冷却好了） public float GetSkillCooldownPercent() { if (skillReady) return 0; return skillTimer / skillCooldown; }第二步：创建爆炸特效类
右键项目 →添加→类，文件名Explosion.cs：
using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using System; namespace MY_FIRST_GAME { public class Explosion { public Vector2 Position; public float Radius; public float MaxRadius; public float Duration; public float Timer; public bool IsAlive => Timer < Duration; public int Damage; public Explosion(Vector2 position, float radius, float duration, int damage) { Position = position; Radius = 0; MaxRadius = radius; Duration = duration; Damage = damage; Timer = 0; } public void Update(float deltaTime) { Timer += deltaTime; float progress = Timer / Duration; Radius = MaxRadius * progress; // 半径逐渐扩大 // 伤害在爆炸瞬间判定（progress < 0.1 时） } public void Draw(SpriteBatch spriteBatch, GraphicsDevice graphicsDevice) { float alpha = 1f - (Timer / Duration); // 逐渐透明 // 画扩散圆环 int segments = 32; float angleStep = MathF.PI * 2 / segments; for (int i = 0; i < segments; i++) { float angle1 = i * angleStep; float angle2 = (i + 1) * angleStep; float x1 = Position.X + MathF.Cos(angle1) * Radius; float y1 = Position.Y + MathF.Sin(angle1) * Radius; float x2 = Position.X + MathF.Cos(angle2) * Radius; float y2 = Position.Y + MathF.Sin(angle2) * Radius; // 简单的线段绘制（用 1x1 像素） DrawLine(spriteBatch, graphicsDevice, new Vector2(x1, y1), new Vector2(x2, y2), Color.Orange * alpha, 3); } } private void DrawLine(SpriteBatch spriteBatch, GraphicsDevice device, Vector2 start, Vector2 end, Color color, int thickness) { Texture2D pixel = new Texture2D(device, 1, 1); pixel.SetData(new[] { Color.White }); float distance = Vector2.Distance(start, end); float angle = MathF.Atan2(end.Y - start.Y, end.X - start.X); spriteBatch.Draw(pixel, start, null, color, angle, Vector2.Zero, new Vector2(distance, thickness), SpriteEffects.None, 0); } public bool Intersects(Vector2 target, float targetRadius) { float dist = Vector2.Distance(Position, target); return dist < Radius + targetRadius; } } }第三步：改造Game1.cs
以下是需要改动的地方：
1. 添加字段：
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private List<Explosion> explosions = default!;
2. 在InitializeGame里初始化：
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explosions = new List<Explosion>();
3. 在Update的 Game 状态里添加技能触发和爆炸更新：
在子弹发射的代码后面加：
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// ★ 右键释放技能 if (currentMouse.RightButton == ButtonState.Pressed && previousMouse.RightButton == ButtonState.Released) { if (player.TryUseSkill(deltaTime)) { player.UseSkill(); Vector2 mouseWorld = camera.ScreenToWorld( new Vector2(currentMouse.X, currentMouse.Y)); explosions.Add(new Explosion(mouseWorld, 120f, 0.5f, 60)); try { shootSound?.Play(); } catch { } // 可换成爆炸音效 } }在粒子更新后面加：
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// 更新爆炸 foreach (Explosion exp in explosions) exp.Update(deltaTime); // ★ 爆炸伤害判定 for (int i = explosions.Count - 1; i >= 0; i--) { if (explosions[i].Timer < 0.1f) // 只在爆炸初期判定一次 { for (int j = enemies.Count - 1; j >= 0; j--) { if (explosions[i].Intersects(enemies[j].Position, 20)) { enemies[j].Hp -= explosions[i].Damage; if (enemies[j].Hp <= 0) { enemies[j].IsAlive = false; score += enemies[j].ScoreValue; enemiesDefeatedThisGame++; particleSystem.EmitHitParticles(enemies[j].Position); // 加经验和掉落判定... } } } } } explosions.RemoveAll(e => !e.IsAlive);4. 在DrawGameWorld里画爆炸：
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foreach (Explosion exp in explosions) exp.Draw(_spriteBatch, GraphicsDevice);
5. 替换DrawGameUI里添加技能冷却图标：
在 UI 最后加：
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// ★ 技能冷却图标 DrawSkillCooldown(_spriteBatch, 700, 500, 40);
6. 添加冷却图标绘制方法：
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private void DrawSkillCooldown(SpriteBatch spriteBatch, int x, int y, int size) { Texture2D pixel = new Texture2D(GraphicsDevice, 1, 1); pixel.SetData(new[] { Color.White }); // 背景 spriteBatch.Draw(pixel, new Rectangle(x, y, size, size), Color.DarkSlateGray); spriteBatch.Draw(pixel, new Rectangle(x + 2, y + 2, size - 4, size - 4), Color.Black); // 冷却覆盖（从下往上） float cooldownPercent = player.GetSkillCooldownPercent(); if (cooldownPercent > 0) { int coverHeight = (int)((size - 4) * cooldownPercent); spriteBatch.Draw(pixel, new Rectangle(x + 2, y + 2, size - 4, coverHeight), Color.DarkBlue * 0.7f); } // 图标文字 _spriteBatch.DrawString(font, "⚡", new Vector2(x + 8, y + 6), Color.Gold); _spriteBatch.DrawString(font, "右键", new Vector2(x - 15, y + size + 5), Color.LightGray); }好了，本节课学习就此结束，我叫魔法阵维护师，关注我，下期更精彩！