Digger is an arcade game that was released by Sega in 1980 and licensed to Gremlin Industries for U.S manufacture and distribution; it runs on their Vic Dual hardware, and is based on Denki Onkyo's Heiankyo Alien (which was released in the previous year and got an enhanced remake on the Game Boy over a decade later). The player must use a four-directional joystick to direct a stick-like explorer around a maze-like canyon, with two buttons to make him dig holes and fill them back up again - and the aliens have been changed into spiders, of which twenty are initially positioned behind that wall on the left side of the screen. On the first round of the game four of them will be let into the playing area; once you have dug four holes, waited for them to fall into them and filled them back up again you will proceed to the second round, on which six spiders will be released. Once you've dug six more holes, waited for them to fall into them and filled them back up again, you will proceed to the third round, on which eight spiders will be released - and this process will be repeated every three rounds thereafter. You will receive a "double-points" bonus, if the red spider falls into a hole you have dug, and you fill it back up again; however, it needs to be the first one on the round, or the red spider will turn green like all the others. You will also receive a 1000-point bonus if you exterminate four consecutive spiders at full point value, during any round - but, if you take too long over a round, all the remaining spiders will be let into the playing area at once, which will almost certainly kill you, unless you're an expert player. When a spider falls into any hole you have dug, it will squeak eight times before it gets out again; five are needed to fill a hole, and if you do not fill it up before the fourth, the spider will get out and kill you.