掌心爆炎：推出那团火的全程

fx-fire

function CreateHandFire(launcher, target)
    local ball = { x = launcher.x + 26, y = launcher.y - 46, trail = {} }

    function ball:Update(dt)
        local dx, dy = target.x - self.x, (target.y - 30) - self.y
        local dist = math.sqrt(dx * dx + dy * dy)
        local step = FIRE_SPEED * dt
        if dist <= step then
            self:Explode(target.x, target.y - 30)
            return false                                   -- 命中: 移除
        end
        self.x, self.y = self.x + dx / dist * step, self.y + dy / dist * step
        table.insert(self.trail, 1, { x = self.x, y = self.y, a = 0.8 })
        for _, p in ipairs(self.trail) do p.a = p.a - dt * 2.4 end
        return true
    end

    function ball:Explode(x, y)
        local boom = CreateBoom(x, y)                      -- 双环扩散 + 核心闪光
        boom:Play(0.5)
        target:OnHit(1)
        ScreenFlash(0.16)                                  -- 一闪即收的屏闪
    end
    return ball
end