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Orbit Defender 2-D (OD2D) is a two-dimensional board game style environment for modeling non-cooperative satellite interactions at a high level of abstraction. The environment was developed by Massachusetts Institute of Technology Lincoln Laboratory (MITLL).
King of the Hill (KOTH) is a symmetric game utilizing the OD2D Environment. This game models a situation in which two opposing groups each have a valuable but unarmed geo-satellite (High Value Asset- HVA) that needs to complete its mission for Earth. There are also ten smaller (Patrol) satellites that can be used to attack the opposing geo-satellite and defend their own to complete the objective of the game.
For an asymmetric game that utilizes the OD2D environment, see GEO Patrol: https://github.com/mpj15/GEO_patrol.
The setup is fixed at the beginning of the game. Both players have the same initial conditions.
The five concentric circles represent the five different orbits. To represent the increase in time it takes to complete one revolution in an orbit farther from the earth, the higher orbits have more sectors and the lower orbits have less sectors. All sectors are numbered to distinguish satellite locations.
The pink satellites (Beta) represent your fleet, and the blue satellites represent the opposing fleet (Alpha). The larger, square satellites represent each player’s “High Value Asset- HVA” (labeled 0), and the ten smaller ones represent the “Patrol” satellites (labeled 1-10). Each HVA and two of the player’s Patrol satellites lie within a highlighted sector at the beginning of the game. This highlighted sector we will refer to as the goal sector.
To score the most points. Gain points by keeping your HVA in the goal sector and use your Patrol satellites to attack and destroy the opponent’s satellites while defending your own before running out of fuel.
Each turn consists of three phases: Movement, Engagement, and Drift. OD2D is a simultaneous move game; that is, both players select their moves for a given turn phase independently, and then the game engine executes the moves for the phase and advances gameplay to the next phase. All moves entered are irreversible.
The three phases are explained more in detail below.
In the movement phase, you can choose to individually move each satellite, including the HVA. You may also choose to keep a satellite where it is. Note that it is beneficial to keep your HVA in the goal sector; see Scoring for details.
The five different actions you can take are No-Op, Radial In, Radial Out, Prograde, and Retrograde.
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No-Op (NOOP) – Short for No Operation. This keeps the satellite where it is.
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Radial In – This moves the satellite into a lower orbit, i.e. the next ring of sectors that is closer to the Earth.
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Radial Out – This moves the satellite into a higher orbit, i.e. the next ring of sectors that is farther from the Earth. Note that the satellite will always move to the outer sector with the lower number (the retrograde sector).
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Prograde – This moves the satellite into the next sector in the same orbit, counterclockwise (up one number).
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Retrograde – This moves the satellite into the previous sector in the same orbit, clockwise (down one number).
The following table shows fuel costs associated with different movement actions.
| Movement | Fuel Cost |
|---|---|
| No-Op | 0 |
| Radial In | 10 |
| Radial Out | 10 |
| Prograde | 5 |
| Retrograde | 5 |
The above image shows what your terminal will look like when you start the game and enter the first movement phase. The “Token” line shows you which satellite you are selecting a movement for. The HVA is zero, and the Patrol satellites are numbers one through ten. To select an action, type the corresponding number and press enter. The game will automatically send you to the movement selection for the next satellite. Continue until you have selected a movement for all of your satellites.
There are also two tables on the side of the board that tell you the current position of each satellite, along with its fuel and ammo status.
In the engagement phase, which occurs after both players have completed their movement phase, you can act against your opponent. These actions can only be completed if you are in the same or an adjacent sector as one of your opponent's satellites. Actions directed diagonally are illegal.
The three actions you can complete are Guard, Shoot, and Collide. The success of these actions depends on the probabilities shown in the tables on the next page. The game processes the engagement outcomes in the following order.
- Guard – This action allows a Patrol satellite to protect its HVA from enemy fire. If the enemy successfully shoots at a HVA, the Patrol satellite protecting the HVA is destroyed instead of the HVA. Guarding takes fuel even if the target satellite is not attacked. Guarding, even if it is unsuccessful, moves your Patrol satellite into the guarded square.
If multiple shots are taken at a guarded HVA, the probability that the guard is successful is changed by (𝑝𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑜𝑓 𝑔𝑢𝑎𝑟𝑑)∗0.5𝑛−1, where n is the number of shots taken at the HVA. In essence, the more times the HVA is shot at, the less likely guard will be a successful move.
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Shoot – This action uses a satellite's single ammo against an enemy satellite. If successful, the opponent satellite will be shot down, and your satellite with survive this engagement. If unsuccessful, your satellite will still lose its ammo.
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Collide – This action allows you to have one of your own satellites collide with an enemy satellite. If successful, both your satellite and the enemy satellite will be destroyed. If unsuccessful, your satellite will now be in the sector of the enemy satellite it targeted.
The following tables show the fuel costs associated with different engagement actions for the same and adjacent sectors, and the probability of success of these actions, respectively.
| Actions WITHIN a Sector | Fuel Cost | Actions against an ADJACENT sector | Fuel Cost |
|---|---|---|---|
| Shoot | 5 | Shoot | 7 |
| Collide | 20 | Collide | 30 |
| Guard | 5 | Guard | 10 |
| Actions WITHIN a Sector | Probability of Success | Actions against an ADJACENT Sector | Probability of Success |
|---|---|---|---|
| No-Op | 1.0 | No-Op | 1.0 |
| Shoot | 0.8 | Shoot | 0.4 |
| Collide | 0.8 | Collide | 0.4 |
| Guard | 0.8 | Guard | 0.4 |
When you start the game and enter the first engagement phase, select an action by typing the corresponding number and press enter. If you select NOOP, the game will automatically send you to the next engagement selection. For each action, the screen will look the same. For shoot or collide, enter the number of the opposing satellite you want to attack. For guard, enter the number of your own satellite that you want to protect. Press enter to save your choice, and repeat for all satellites. If you make an invalid selection (ie. an illegal move) the game will tell you and will force you to select a legal action.
Engagement outcomes are displayed both players have completed the engagement phase. As stated before, the guard outcomes are determined before the shoot outcomes, and shoot is determined before collide. For guard, if it is successful, then the guardian becomes the target and the HVA will not be hit.
The drift phase, which happens immediately after the engagement phase has been completed, the earth spins and every satellite on the board shifts one sector counterclockwise. This means that the two goal sectors for each player will always be directly across the board from one another, and satellites in different orbits will move different amounts due to varying sector size.
Points are added to the total score for each player at the end of every turn.
The HVA starts the game in its goal sector, and it is to your benefit to keep it there for as much of the game as possible. The HVA models a geo-satellite which must maintain a specific longitude (the longitude of the goal sector) to perform its mission. HVA, but it is in an adjacent sector to the goal sector, you will receive three points. If the HVA is in any other sector, you receive no points. The only way you can score points during the game is through the HVA’s position.
The initial score is 200 points. Each satellite starts with fuel of 100. The total fuel of the Patrol satellites, 100, is divided by how many Patrol satellites there are, 10; these sum to 100 points. This is then added to the total fuel from the HVA, which is also 100 points. (100+100=200) After each turn, the score is recalculated by the new fuel sum from the 11 satellites. When a satellite dies, it’s fuel is automatically decreased to 0.
Each satellite will lose one fuel per turn regardless of which movements or actions that satellite completes.
To win the game, you must have a total score of 250 points.
The game ends when one player’s HVA is destroyed or when a HVA completes its mission (it attains the high score of 100 points). Alternatively, it can also end when the turn limit (50) is reached. There is a draw if both players have the same number of points when fuel runs out or when both players reach 100 points at the same time.
The satellites will always drift one sector counterclockwise before the end of every turn (after the movement and engagement phases). Consider where you will drift ahead of time and where you want your satellites to end up.
Satellites can be moved radially inward or outward. Though it costs fuel to move inward, the period of orbits closer to earth are much smaller. Therefore, it will take you less turns to move around the board.
The HVA is your main asset; losing your HVA (either through running out of fuel or having it blown up) terminates the game. Avoid moving your HVA because you lose fuel in the process. With that in mind, consider keeping a few satellites in the same sector as your HVA to avoid vulnerability.