P.E.M.D.A.S., The Order of Operations
Apply your knowledge of the four operations (addition, subtraction, multiplication, division) to crack the attacking Roborator's shield codes and then blast them into scrap metal!
Instructions
Game Goals
This maths game helps with division, multiplication, addition and subtraction  essential skills for BIDMAS, the order of operations.
Roborators were created to help us, but Professor BIDMAS has infected them with a virus: they now classify all human life as litter and plan on eradicating mankind. You must hurry to the Roborator factory and destroy the Roborators with your powerful weapons.
The Roborators are equipped with shields, which you can deactivate with your arithmetic codecracking skills. Blow up Roborators to gain experience points and earn bounty money.
The cash can be used to buy more powerful weapons in the shop, and the experience points are required to clear the level.
How To Play
You must clear five different stages, each corresponding to a different part of the factory, in order to vanquish the Roborator menace. In each stage, Roborators will spawn and advance slowly towards you. Each Roborator has a code, or formula, displayed above its head: you must type in the answer to this formula to disable the Roborator's shield and blast it.
There are four classes of Roborator (green, purple, yellow, and red), which get progressively harder within each stage. If you achieve a 'Combo' of nine consecutive correct answers for any given Roborator class, then the next, higher class of Roborator appears. The tougher Roborators are worth more experience points and higher cash values (see below).
You get four Lives in each level, which are lost one at a time with blows from the advancing Roborators. An incorrect answer results in loss of time but not loss of a life.
Your selected weaponry appears in the bottomleft of the screen. Switch weapons and ammunition to fire more rapidly or unleash greater destructive power.
Game Controls
You may enter answers either using the keyboard, or by clicking on the number pad in the bottomright of your screen.
Weapons may be selected by clicking on the weapons interface in the lowerleft side of the screen or using the hotkeys below:
Weapon  Hot Key  Description 

E  Entrylevel firepower  weak and slow.  
R  More effective weapon for pinpoint accuracy  
T  Devastating antimech weapon with multiannihilation capability. Experienced personnel only.  
Z & X  Different types of ammo have very different explosive powers.  
Q  Blows up all Roborators onscreen but does not count towards experience points or bounty money  
S  Briefly shows answers to all formulas onscreen.  
W  Electric wall that destroys any robot that touches it. Does not count towards experience points or bounty money.  
A  Slows down all Roborators for a short time 
Stages
The factory contains five stages, and you graduate from one stage to the next by earning sufficient Experience Points (as shown by the meter on the right side of the screen filling up):
Stage  Math Content 

Training Ground  Addition 
RoboBarracks  Subtraction 
Assembly Line  Multiplication 
Weapons Store  Division 
Prof's Lab  Addition, Subtraction, Multiplication, Division 
Scoring
You earn cash for destroying Roborators (Hit $ ) and for demonstrating consistency in your codecracking ability (Combo $ ):
Hit $
The Hit $ value earned for destroying a Roborator depends on the Roborator's class and the speed with which you calculate its code:
Hit $ = $ 25 × Roborator Class × Distance FactorDistance Factor depends on how far the advancing Roborator is away from you when blasted. Distance is used as a proxy of your speed of calculation, i.e. if you destroy a Roborator when it's far away, you score the highest Hit $ score. The range of values for Roborator Classes and the Distance Factors are:
 Roborator Class

Value = 1 Value = 2 Value = 3 Value = 4  Distance Factor

Near Medium Far Value = 1 Value = 2 Value = 4
For example: a Yellow Roborator hit at a medium distance is worth: $ 25 × 3 × 2 = $ 150, whereas a Red Roborator hit at a far distance is worth: $ 25 × 4 × 4 = $ 400.
The cash earned from destroying Roborators in a stage is the cumulative sum of all Hit $ in that stage, i.e. ∑Hit $ .
Combo $
The Combo $ bonus depends on the Roborator's class and the number of consecutive correct answers (3, 6, or 9):
Combo $ = $ 100 × Roborator Class × Combo FactorThe range of values for Roborator Classes and the Combo Factors are:
 Roborator Class

Value = 1 Value = 2 Value = 3 Value = 4  Combo Factor

Combo × 3 Combo × 6 Combo × 9 Value = 1 Value = 4 Value = 20
For example: destroying six Purple Robots without making any mistakes is worth: $ 100 × 2 × 4 = $ 800, whereas destroying nine Yellow Robots without making any mistakes is worth: $ 100 × 3 × 20 = $ 6000.
The cash earned from demonstrating consistency in a stage is the cumulative sum of all Combo $ in that stage, i.e. ∑Combo $ .
Thus, the total cash earned in a stage is:
Improve your score
Basic Strategies
Don't let Roborators get too close. The further away they are when you blast them, the more cash you earn: a "Far" Roborator is worth 4 times more than a "Near" one.
Combos can boost your score quickly. Focus on getting as many consecutive correct answers as possible. Combo x 9 gives you the maximum bonus and brings on the next Roborator class.
Higherclass Roborators are worth more money and earn more experience points per hit. Try to get to the red Roborators as quickly as possible, with as many lives to spare as possible.
Your ComboCounter gets reset if you enter an incorrect answer or lose a life. You have four Lives that get replenished at the end of the stage. It is often worth risking a life or two to get the extra few seconds to work out the right answer.
Weapons
Save the best weapons for the toughest Roborators:
 MemoRay
 This the most valuable weapon, as any Roborators destroyed using it count towards both the dollar value and experience points earned for clearing the stage. Use it when there are multiple Roborators on the screen to maximize its value.
 Rocket Launchers
 In multiannihilation mode this destroys two Roborators with one answer, but does not provide additional experience points. It has a max ammo limit of 50 rockets, so keep an eye on your rocket inventory.
 Grenades
 These are very powerful, as they clear all Roborators onscreen. However, like the ElectroWall, it does not contribute towards cash earned or experience points. Use them wisely!
Math Strategies
In each stage the math gets tougher and tougher, so here are some expert survival tips!
 Training Ground
 Try to use "number bonds" that make 10. For example: 14 + 26. Notice that 4 and 6 always go together to make an extra 10. When adding numbers together, try to add the tens together and then the units. For example: 14 + 15. Do 10 + 10 = 20, then 4 + 5 = 9. So the answer is 29.
 Robo Barracks

When subtracting, it is sometimes easier to ‘add on’. For example, 27 − 19. How many do you add onto 19 to make 27? Answer: 8. This might be easier than taking 19 away from 27.
 Assembly Line

Anything multiplied by zero always makes zero.
Multiplying by 2 is the same as doubling.
Multiplying by 3 is the same as trebling.
Multiplying by 4 is the same as doubling and then doubling again.
To multiply by 10, just add a zero to the end of your number.
Multiplying by 5 is the same as multiplying by 10 and then halving.
When you multiply by a number close to 10 try using this strategy: Let’s calculate 9 × 8, for example. Do 10 × 8 = 80. Then subtract 8 to make 9 lots of 8. Answer: 72.
 Weapons Store

It's sometime useful to think of dividing in terms of multiplication. For example, 15 divided by 5 is the number that you have to multiply 5 by to get 15. The answer is 3 because 3 × 5 = 15.
 Prof's Lab

When a number is very close to 100 you might use the method of 'borrowing'. Take 78 + 97, for example. You only need 3 extra to make 97 into 100. So you 'borrow' 3 from 78. So the question is now the much easier 75 + 100. Answer: 175.
When you multiply numbers that end in zero you can ignore the zero to begin with. For example, 12 × 20. Work it out as 12 × 2 to make 24. Then add an extra zero to make 240.
When you divide numbers that end in zero you can ignore the zeros. For example, 120 ÷ 20 gives the same answer as 12 ÷ 2.