local frame = CreateFrame("Frame", nil, UIParent);
frame:SetFrameStrata("TOOLTIP");

local texture = frame:CreateTexture();
texture:SetTexture([[Interface\Cooldown\star4]]);
texture:SetBlendMode("ADD");
texture:SetAlpha(0.5);

local x = 0;
local y = 0;
local speed = 0;
local function OnUpdate(_, elapsed)
  local dX = x;
  local dY = y;
  x, y = GetCursorPosition();
  dX = x - dX;
  dY = y - dY;
  local weight = 2048 ^ -elapsed;
  speed = math.min(weight * speed + (1 - weight) * math.sqrt(dX * dX + dY * dY) / elapsed, 1024);
  local size = speed / 6 - 16;
  if (UnitAffectingCombat("player")) then
    if (size > 0) then
      local scale = UIParent:GetEffectiveScale();
      texture:SetHeight(size);
      texture:SetWidth(size);
      texture:SetPoint("CENTER", UIParent, "BOTTOMLEFT", (x + 0.5 * dX) / scale, (y + 0.5 * dY) / scale);
      texture:Show();
    end
  else
  texture:Hide();
  end
end
frame:SetScript("OnUpdate", OnUpdate);

local size = speed / 6 - 16;