Boulder Dash, according to the article on Wikipedia, was one of the very few games that were designed first for the home PC and only later remade for the arcade, and not the other way around. Rockford was the home conversion of the officially-licensed arcade game.
The game has been expanded from a simple diamonds-and-rocks game to feature five characters in five different settings: an explorer in the South American jungle (the toucans were a dead giveaway), a cook, a cowboy, an astronaut and a surgeon. There are four levels to each of the worlds. You collect coins while dodging or killing enemies – you can only enter a gate to the next level if you have the required number of coins. You can kill enemies by dropping rocks or coins on them; you’ll die if they touch you or if a coin or rock falls on you in turn. There are usually two types of moving enemies in each world: ones that explode into coins, and ones that just explode. So frequently, passing the level entails killing as many of the right kind of enemy as you need and collecting the coins. It’s a colourful concept with an elegant variation in level types across all five worlds.
There’s no real music except the intro and an annoying tune when you a) die or b) pass a level. The sound-effects are on the internal speaker, so there’s just the chinking noise of falling coins (or a thud in the case of rocks), a repetitive and pointless footstep sound and the noise of an explosion when something falls on you. Explosions cover a square of nine tiles, so make sure you aren’t too close to one when it happens.
There’s a lot of humour in each situation. The surgeon is especially funny. You are chased by rolling skulls or butterflies made of two purplish ears (icky, but at least they aren’t brains or kidneys), and the rocks become large, creepy eyeballs. The walls are red with disembodied sets of teeth grinning at you. After a while you feel vaguely queasy, as though trying to watch CSI while eating curry (don’t try this). The spaceman was my favourite – you dodge spinning galaxies and what looks like a cross between yellow chickens and the Starship Enterprise, collecting suns along the way. The rocks are really little planet Earths. The third level is the only one to feature the amoeba, which can trap you if you stray too close to it. It causes enemies to blow up into coins by the score.
There are also strange worm-like creatures with the power to turn coins into rocks (or vice versa). The cowboy world has a wagon train with a horse on either end, while the cook has both pizza and burger chains (the burger turns oranges into apples – i.e. coins – and the pizza turns oranges into fried eggs – which can kill you as they fly around.)
What makes the game fun is the element of pressure – there’s only a limited amount of time available for each level, and there is some degree of challenge in the placement of coins and obstacles in the level. After a while it becomes instinctive (I sometimes feel I could play it with my eyes closed) but at the same time there is enough uncertainty to keep you interested in competing with your previous scores. The gameplay can be infinite because you receive a 1up for every 40 000 points you collect, and when you complete one world you can simply start another. Unfortunately, there’s no hall of fame for this game.