Difference between revisions of "Commander Keen: Galaxy"

Revision as of 13:49, 30 May 2014

This page discusses features found in Episodes 4-6 and Keen Dreams of the Commander Keen series. For game-specific routing, check the appropriate game page:

Commander Keen: Secret of the Oracle

Commander Keen: The Armageddon Machine

Commander Keen: Aliens Ate My Babysitter!

Commander Keen Dreams

Game Control

If we compare to the Vorticon engine, the Galaxy engine is a large improvement in terms of control: more responsive, smoother, and not bogged down by limited commands (i.e., two-button firing). This means that maneuvers are a lot more flexible, especially when handling enemies. It does, however, mean that the speedrun is expected to perform far more optimally, and the current Keen runs are well-optimized. Some of the expected optimizations will be discussed in this topic, although they will be mentioned on a per-level basis as well.

Horizontal Movement

On the ground, Keen has no momentum: pressing left/right makes Keen move right instantaneously and at maximum horizontal speed, and switching direction incurs no time penalty.

In the air, Keen's momentum from the Vorticon engine returns: it takes time to build up to maximum speed and to switch directions. It is, however, not nearly as slow to do so, and so maneuvering in mid-air is quite doable (and sometimes necessary).

Slopes: There are two types of slopes, gradual and steep, and they affect the speed at which Keen walks. Specifically, Keen's speed changes by 1/6 on gradual slops and by 1/3 on steep slopes, either decreasing when walking up the slope or increasing when walking down the slope. Thus, Keen should always jump/pogo up slopes (thereby ignoring the speed change) and walk down slopes (taking full advantage of the faster movement).

Vertical Movement

Entering the air, whether through a jump or a pogo bounce, takes three frames. Generally this isn't of great importance, but it's a good rule of thumb to only jump when necessary.

Jumping: Keen's jump has no preparation time, and the height can be controlled for as long as roughly the first half (in time, not distance) of the ascent. The gradation of variability is very small, meaning you can time jumps almost to any pixel height: for normal jumps this isn't often an issue but it can be useful for jump shots (see "Firing").

Pogoing: Similar to the normal jump, except that Keen achieves a much greater height and has a significant fixed-height minimum. The pogo can be activated and deactivated at any time: activating on the ground automatically begins a pogo jump. As in the Vorticon engine, pogoing preserves horizontal momentum: unlike the Vorticon engine, continuous pogoing does not take extra time to start and therefore doesn't lose horizontal momentum at all, so if you need to jump somewhere you can gain a small amount of time pogoing the entire way there rather than jumping after landing.

Keen's hitbox is slightly shorter when pogoing, which can occasionally be taken advantage of during constrained jumps.

Impossible Pogo Trick (IPT): Pogoing then jumping from the ground, at about the same time, causes you to jump slightly higher than a full-height pogo jump normally would allow. This is an extremely important trick as the developers intentionally included quite a few shortcuts that are only possible with the IPT. There are two variations:

• A moving IPT is done while walking: the timing is loose enough that you can actually press both pogo and jump at the same time and still pull off the IPT.
• A standing IPT is done without any horizontal movement: the timing is far more precise, though it's used less often. (Based on the game help, this variant wasn't intended, which may explain why it's harder to do.)

Chaining Jumps: Since Keen's vertical momentum is very gradated, it's actually possible to land on a floor from below without "falling" onto that floor: in other words, spending zero extra time in the air. Jumping vertically from platform to platform is a very tricky maneuver and optimizing the height of these jumps is very important, as you'll be doing it often and the time adds up quickly. This is most noticeable (and used) on platforms you can jump through.

Grabbing Ledges: If Keen is next to but below a ledge in mid-air, pressing the direction towards the ledge will cause Keen to grab that ledge: pressing up or same direction will then cause Keen to climb up to the floor above, while pressing down or the opposite direction will cause Keen to fall instead. As with chaining jumps, there is a pixel-perfect height at which Keen will grab the ledge without extra air time, though this doesn't occur as often. Generally, however, grabbing ledges should be avoided whenever the ledge can be cleared entirely in order to reach the floor itself, since climbing the ledge takes time.

Firing

Keen can fire in any cardinal direction: left/right, up, and down (in the air only). Similar to the Vorticon engine, firing halts horizontal momentum, but it takes roughly a quarter of a second in the Galaxy engine so it is less significant. Furthermore, there's no mid-air firing stance, so you can keep moving in the air without losing any momentum.

Jump Shots: Ideally, you should always be in the air when firing. This leads to jumping from the ground in order to shoot, usually considered a "jump shot" since it's different from shooting while you happen to already be in the air. Making sure a jump shot works means the shot has to fire before you land: if you're beginning to fire but no shot occurs, you'll be stuck landing and entering firing stance, wasting time. Depending on the enemy's height, jump shots can be easy, hard, or impossible.

Glitches

The most interesting glitches in the Galaxy games are actually game-specific, so check appropriate pages to learn more. The glitches detailed here apply across all games and all versions (or specific versions as noted).

Corner Boosting

Moving/landing onto the edge of a platform in a precise manner allows Keen to clip through a little bit of the platform, boosting his movement for an instant. Because of the precision involved this is typically unintentional but has practical applications in some specific cases.

Clipping Through Walls

Throughout the Galaxy games, there are instances of poorly-placed terrain and collision detection such that Keen can either move entirely or partially clip through supposedly-solid walls. Useful instances of such terrain will be explained on a per-map basis.

When clipping through solid walls, the Galaxy engine chooses to prioritize moving Keen up and to the right to find a non-solid space to occupy.

Another wall-clipping possibility has to do with Keen's sprite positioning. Depending on his animation state, Keen's collision box can be different: when applied from the looking-down state to the falling state, for instance, Keen's collision box will shift upwards. If Keen is pushed into a ceiling while looking down, he will enter his falling state but be stuck inside the wall, at which point clipping movement rules apply. This can be similarly done during the first frame of Keen's walking state.

Exiting Out of Bounds

Levels automatically include exit-level triggering just outside the viewable level boundaries on the left and right sides. In some levels this is an important feature as it's the intended way to leave the level. While not useful by itself, there are a few ways of glitching out of bounds that will thereby allow Keen to trigger the exit of a level prematurely. Note that exiting a level this way does not trigger anything else such as gaining items or rescuing people.

Wrong Door

Walking through a door places Keen at a particular coordinate, not to a particular door/object: the default coordinate is the upper-leftmost point on the map. Although most doors are assigned a new coordinate, there are a few doors in the Galaxy games that have no such assignment (perhaps due to not expecting Keen to be able to use those doors). Consequently, the upper-leftmost point on the map is always out of bounds, so Keen automatically finishes the level. This is only seen in Keen4 but can theoretically apply to other cases.

Death No-Clip

Also known as the "save/load glitch". When Keen is struck by an enemy, his "death" flag is set and, among other things, he ignores terrain collision while moving horizontally. By saving after Keen is struck but before the game's restart dialog is opened, then reloading the game from that point, Keen's death is reset but is otherwise unchanged: his horizontal, terrain-ignoring self can then be used to go out-of-bounds and (with the above glitch) exit the level.

Part of dying includes a sound effect: this sound effect is forced to end before exiting the menu (accessed when saving/loading). To minimum time spent in the menu, it should be accessed late into the sound effect so that no time is wasted waiting for the sound to end. As a rule of thumb, wait until Keen is lower than he was when he died before going to the menu.

Platform Teleporting

Whenever Keen is standing upon a platform (that is, the specific sprite type that acts like terrain), his state is tied to that platform. If, in the extremely rare case, the platform Keen is currently standing on disappears from the map, Keen will be instantly placed (or teleported) on the next available platform that occupies the same vertical position that the old platform used to be.

By itself, this has no apparent application in any of the games. However, this teleportation also appears to apply to Keen's bullets and enemy laser bullets, leading one to the conclusion that such bullets are considered platforms for the sake of this glitch. It is also the basis of the Impossible Bullet Trick in Keen6.