This
game is a blend of the computer vs. tank battle from Combat, the tunneling of
Dig Dug and target shooting of Carnival.
The objective is to tunnel your way to get a clear shot at the targets. These are called “nuclear bases” and must all be destroyed in order to complete the round. Your screen weapon is known as the “core capsule”. Standing guard are two “core ranger tanks” that approach from the sides at the top. They are constantly firing and chasing you through any open tunnels. There are a variety of hidden bonus items waiting to be discovered. It is definitely worth looking for: the shovel, walkie-talkie, flag and key. There will be only one per screen and are worth from 1,000 - 4,000 points. Tanks are worth 50. Bases vary from 50 to 7,550 depending on the level diffficulty and if the hidden token is found. The pace of the game increases along with the round. Some of the higher rounds have no tunnel walls showing. So it looks like you are out in the open. The targets may also be presented one at a time in any of the slots at the top of the screen (above ground). Some rounds continue where the last screen left off. This may have been due to time running out.
All of these screen changes along with different combinations of enemies help to reduce some of the redundancy. As a result the game seems more spontaneous. There are two types of enemy tanks: the white Sentries and the blue Diggers.
The tanks always move faster than you. They will increase their speed and start drilling their own tunnels as you progress. You can take out a tank by hitting it with cannon fire, but it will be replaced in a short time. You don’t have to worry about the exploding debris, but it can block shots. The white tanks can’t immediately detect your presence and will turn and fire randomly. If you are directly facing them, they will open fire. The blue tanks are much tougher. If you cross their plane in any way they will turn and come after you. You are awarded a bonus tank for every level, but 4 rounds constitute one level. In the higher rounds you have to pay as much attention to the blue tanks as to you would to the energy source targets. Let them come down at you, but get out of their direct path and nail them before they can turn. They are definitely a menace! They are relentless and distracting. There is a third tank at the bottom of the screen which is the timer. If it reaches any of your replacement tanks you lose a life. The highest I ever got was Round 21 at 200,000+ points.
The game is actually fun and challenging and it requires some strategy. But, it may be a little too one-sided due to the strength and speed of the enemy.
The artwork on the box, instructions and cart shows your typical artistic exaggeration. The actual game is hardly that dramatic looking. The artwork shows a space ship blasting away at tanks within a 3-D maze. The maze looks like it has been predefined and seems more above ground than below. Maybe the artist was more influenced by the valleys and channels of the Death Star in Star Wars. Thunderground is subtitled the “official arcade version”. It may well have been an arcade machine, but I don’t remember it. The 2600 is the only home system where I have seen this game appear.
There is a pirate version of this cart. I believe is in PAL. I have seen it on multicarts. Probably done in Taiwan, no doubt. In order to hide the telltale scrolling Sega logo & copyright date on the title screen, they changed the graphics to show a row of 4 scrolling tank-like objects instead. I don’t know if they bothered to rename the game or not. Should this be considered a collectible version? I am inclined to say no. The game play is the same. There are many different games that have been pirated and have and have the company logo blocked out or altered in some fashion. Activision and Atari, being among those that I have seen. This is obviously to be a little less blatant and avoids immediate attention from lawyers. I do believe in collecting those carts in which the game play or game graphics have been changed. These can provide a slightly different feel. They may even be more challenging in some instances.
