This is the first full-length Commander Keen game on the new game engine. This engine would last through to Keen 6, but this game shows rather nicely what the engine can do. While Keen 3 got a little stale for platformers of the era, Keen 4 brings the series right to the forefront of best 2D platforming games for PC at the time.
The first thing you will notice starting the game is the overworld looks much better. I’m not sure if resolution has increased, but everything is more detailed. This carries through to the first level, in which there are houses to enter and underground passages to traverse. You’re still collecting foods like candy bars, soda pop, donuts, and ice cream cones, but you’re also collecting drops of water, and later on, jars of water. The water drops don’t contribute to your score, but collect 100 and you get an extra life. A jar of water is an instant extra life. All food items still give extra lives at set score numbers, and add to your overall score.
Actually, this game is much more generous with extra lives, as well as ammunition, which makes it easier than previous games. You soon realize you need to rescue Oracles – men with white beards who are very wise – and upon rescue, they simply say they will go to the Oracle Chamber. Spoiler alert, the Secret of the Oracle is revealed at the end of the game.
Each level has a unique look, which is something the team was trying for with Keen 3, and something the team was not trying for at all with Keen 1 and Keen 2. A couple of levels are dotted with houses, there is an ice level and pyramid levels. A fun level is called “Miragia,” in which platforms appear and disappear as if they were a mirage. Compared to endless red or blue platforms in the first two games, the level variety in this game is a most welcome departure.
By the end of the game, you will have rescued eight Oracles, who share their knowledge. It’s pretty apparent Keen 5 has not begun development, as iD Software asks you to send them a letter, asking about Commander Keen 5, without asking you to send money for a purchase. There is no final boss in Keen 4. That said, it’s a beautiful tech demo and a fun game for 1991, and is the start to a superb trilogy with Keen 5 and Keen 6 included. Definitely recommended.