Example HUD for GMod (with scale)

cl_hud.lua

local font = "PF Ronda Seven"

surface.CreateFont( "Microblast_BarText", {
	font = font,
	size = 20,
	weight = 500,
	blursize = 0,
	scanlines = 0,
	antialias = false
})

local bgColor = Color(31, 31, 31)
local emptyColor = Color(128, 128, 128)
local redLow = Color(251, 96, 80)
local redHigh = Color(201, 46, 30)

local scrWidth = 1920
local scrHeight = 1080

local multX = ScrW() / scrWidth
local multY = ScrH() / scrHeight


hook.Add("HUDPaint", "Microblast", function()
	local hpBg = {
		{x = 50 * multX, y = 1010 * multY},
		{x = 510 * multX, y = 1010 * multY},
		{x = 530 * multX, y = 1040 * multY},
		{x = 70 * multX, y = 1040 * multY}
	}

	surface.SetDrawColor(bgColor)
	surface.DrawPoly(hpBg)

	for i = 0, 9 do
		local block = {
			{x = (60 + i * 45) * multX, y = 1015 * multY},
			{x = (100 + i * 45) * multX, y = 1015 * multY},
			{x = (115 + i * 45) * multX, y = 1035 * multY},
			{x = (75 + i * 45) * multX, y = 1035 * multY}
		}

		if i <= 2 then
			if LocalPlayer():Health() >= (i + 1) * 10 then
				surface.SetDrawColor(redHigh)
			else
				surface.SetDrawColor(redLow)
			end
		else
			if LocalPlayer():Health() >= (i + 1) * 10 then
				surface.SetDrawColor(color_white)
			else
				surface.SetDrawColor(emptyColor)
			end
		end

		surface.DrawPoly(block)
	end
end)


local toHide = {
	["CHudHealth"] = true,
	["CHudBattery"] = true,
	["CHudAmmo"] = false,
	["CHudSecondaryAmmo"] = false
}

hook.Add("HUDShouldDraw", "MicroblastHide", function( name )
	if toHide[name] then
		return false
	end
end)