Xevious (NES) Mesen Lua script that shows bombable objects

Xevious - show bombable objects.lua

-- xevious NES Mesen "show bombable objects" Lua script
-- coded by karmic, july 10 2021
-- slightly improved jan 21 2022

function read(addr)
  return emu.read(addr, emu.memType.cpuDebug)
end

function readbeword(addr)
  lo = read(addr+1)
  hi = read(addr)
  comb = lo | (hi << 8)
  if hi >= 0x80 then
    return 0 - ((comb ~ 0xffff) + 1)
  else
    return comb
  end
end

function drawrect(x, y, width, height, color)
  emu.drawRectangle(x, y, width, height, color, false, 0)
end

function main()
  emu.clearScreen()
  
  -- game must be in main game mode
  if read(0x10) ~= 2 then return end
  
  -- magenta, moving enemies
  for obj = 0,7 do
    if read(0x500 + (obj*0x10)) ~= 0 then
      x = read(0x504 + (obj*0x10))
      y = readbeword(0x506 + (obj*0x10)) + 1
      drawrect(x, y, 0x10, 0x10, 0xff00ff)
    end
  end
  
  -- cyan, stationary and hidden targets
  for obj = 0,0x0f do
    if read(0x300 + (obj*0x8)) ~= 0 then
      x = read(0x303 + (obj*0x8))
      y = readbeword(0x301 + (obj*0x8)) + 1
      drawrect(x, y, 0x10, 0x10, 0x00ffff)
    end
  end
  
end


emu.addEventCallback(main, emu.eventType.startFrame)