Metroid Fusion - Drops Predictor

rns = { 256, 512, 512, 0, 768, 256, 512, 512, 512, 0, 512, 0, 0, 768, 256, 0, 768, 256, 768, 768, 0, 512, 768, 0, 768, 256, 0, 768, 256, 256, 256, 512 }
enHealth = { }
display = { "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "" }
dropsX =  { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  -- 00
            0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0,  -- 10
            0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0,  -- 20
            0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0,  -- 30
            0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  -- 40
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0,  -- 50
            1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1,  -- 60
            1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,  -- 70
            1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0,  -- 80
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  -- 90
            0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0,  -- A0
            0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0,  -- B0
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }    -- C0

function DrawArrow(x, y)    -- displays an arrow
    gui.text(7+x, y, "<-")
end

function DrawDrop(x, y, label)
    if label == "Y" then
        gui.text(x, y, label, "#F0F000")
    elseif label == "G" then
        gui.text(x, y, label, "#00F000")
    else
        gui.text(x, y, label, "#F00000")
    end
end

while true do
    -- get these values every frame
    local cameraX, cameraY = memory.readword(0x3001228), memory.readword(0x300122A)
    local frame1 = memory.readbyte(0x3000BE5)
    local frame2 = memory.readword(0x3000002)
    local fullHealth = (memory.readword(0x3001310) == memory.readword(0x3001312))
    local fullMissiles = (memory.readbyte(0x3001314) == memory.readbyte(0x3001316))

    -- display frame counter for convenience
    gui.text(28, 3, 255 - (frame1 + 45) % 256)

    -- for each enemy
    for i=0,23 do
        local status = memory.readword(0x3000140 + i*0x38)
        local prop = memory.readbyte(0x3000174 + i*0x38)
        local id = memory.readbyte(0x300015D + i*0x38)

        -- if enemy exists and can drop x
        if status > 0 and prop < 0x80 and dropsX[id + 1] == 1 then
            -- get enemy position
            local enemyX, enemyY = memory.readword(0x3000144 + i*0x38), memory.readword(0x3000142 + i*0x38)
            local posX, posY = bit.rshift(enemyX - cameraX, 2), bit.rshift(enemyY - cameraY, 2)

            -- update enemy's past/current health
            local pastHealth = enHealth[i+1]
            local enemyHealth = memory.readword(0x3000154 + i*56)
            enHealth[i+1] = enemyHealth

            -- if enemy recently died, show drop
            if pastHealth == 0 then
                DrawDrop(posX, posY, display[i+1])
                DrawArrow(posX, posY)

            -- otherwise, determine which x will be dropped
            else
                local healthX = memory.readword(0x82E4D54+ id*0xE)
                local missileX = memory.readword(0x82E4D56 + id*0xE)
                local redX = memory.readword(0x82E4D58 + id*0xE)

                local temp1 = (frame1 + 45) % 256
                local temp2 = bit.rshift(frame2 + 45, 4)
                local rn = rns[((i + temp1 + temp2 + enemyX + enemyY) % 32) + 1]
                local cmpVal = rn + temp1
                local cmpRed = 1024 - redX

                local dropLabel
                if cmpVal >= cmpRed then
                    dropLabel = "R"
                elseif cmpVal >= cmpRed - missileX then
                    if (fullMissiles and not fullHealth) then
                        dropLabel = "Y"
                    else
                        dropLabel = "G"
                    end
                else
                    if (fullHealth and not fullMissiles) then
                        dropLabel = "G"
                    else
                        dropLabel = "Y"
                    end
                end

                DrawDrop(posX, posY, dropLabel)

                -- if enemy just died, save drop and draw arrow
                if enemyHealth == 0 then
                    display[i+1] = dropLabel
                    DrawArrow(posX, posY)
                end

                -- determine when red x will appear
                if redX > 0 then
                    local wait = 0
                    while temp1 ~= 0 do
                        rn = rns[((i + temp1 + temp2 + enemyX + enemyY) % 32) + 1]
                        if rn + temp1 >= cmpRed then
                            gui.text(posX, posY + 7, wait)
                            break
                        end
                        wait = wait + 1
                        temp1 = (temp1 + 1) % 256
                        if (temp1 % 16 == 0) then
                            temp2 = temp2 + 1
                        end
                    end
                end

            end
        end
    end

    vba.frameadvance()

end