TED5, the level editor for Commander Keen 4 through 6, as well as Wolfenstein 3D and numerous Apogee games, unlike popular belief, is quite easy to use--once you get used to it's unusual interface. Coupled with various fan-made utilities, Keen fans are now able to build custom levels for Keens 4 through 6. Recently, fans, while in the process of making custom levels, have stumbled across some unusual bugs they can exploit in their levels. Sample a few of these...
Impossible Bullet in Keen 5?
Free falling platforms, by nature do not care if a solid (foreground block) is in the way or not; without an Info-layer, "B" tile, a falling platform will happily drop for the rest of it's life--even through solid foreground tiles! Unfortunately, once it drops off the bottom of the level, it ceases to exist. Yet the in-game ?object? remains, and is happy to stay exactly where it was last used--granted a certain super-hero is still standing on it. Keen, on the other hand, has a moral obligation to NOT go through solid foreground blocks, such as the bottom of the level, unless specifically asked to. Therefore, in such a case, the blockless platform drops off the map, and Keen is left standing on the first solid block he meets in his descent, the in-game platform ?object? waiting patiently beneath his feet. An excellent time to do Impossible Bullet! Impossible Bullet can be achieved by either Keen firing upwards, or letting a gun,directly below keen, fire. Aesthetically speaking, a platform that falls through a hole in the floor instead of through a solid floor is preferable, but of course, it's up to you, the level designer.
The Matrix "close the door and it opens to someplace else" trick
Yes, my friend, you can copy parts of the Matrix in your favorite side-scrolling PC game. Here's how. Things you'll need: a slider switch and a whole lot of tweaking. If a switch is linked to the bottom left block of a door (not the door frame--the black part inside the door), Keen, instead of exiting in the original addressed location, will exit in an entirely different place--when the you flip the switch. Apparently, the original and modified exit locations pivot around coordinates ($xxxx, $000F/$002F/$004F...). When the original is above one of these y coordinates, the modified exit will be below it, and vice versa. It seems that the farther away from the pivoting y coordinates the original exit is, the farther in the opposite direction the y coordinates for the modified exit becomes. Currently no explaination for phenomenon has been worked out, so we are reduced to the primitive method of trial and error when using it.
The QED, it doesn't break when it explodes!
Fact one: the damage tiles for the QED will only show up in one location in the level ($0010, $000B)--it's hard coded into the game. Fact two: the QED does absolutely nothing in any level other than level 12; it simply won't blow up anywhere else. Given those two facts, it is easy to figure out how to trigger the endgame sequence. On a side note, you CAN place the QED anywhere in level 12, and it WILL trigger the endgame sequence when a Shikadi mine explodes nearby. It just won't show any damage unless it is located at ($0010, $000B).
h4x0ring the level map
The four elevator doors pose a problem when creating a custom level map. While you can create perfect elevator shafts anywhere in the level map, the four original doors will always exist, and if you put foreground tiles where they were in the original map, it is likely they will make an appearance, as gaping black holes, or some other combination of un-wanted tile, at some point in the game. Actually, the foreground tiles at($0000, $0000) ($0000, $0001), ($0001, $0000), and ($0001, $0001) are blocks that show up. To prevent such a disaster, keep the foreground tiles in the top left corner blank, and make sure you have only background tiles where the original elevator doors were. The original elevator door locations are (top left corner): lower elevator: $0018, $004C middle left elevator: $0016, $0037 middle right elevator: $001A, $0037 top elevator: $0018, $001E Keep track of those locations in your level map and you'll be fine.
Flip a switch and diamonds and hazards disappear! Walk on thin air! Here are a few other clever things you can do. Fire spinners (for lack of a better name) can be switched off using a slider switch. Make sure there are at least 9 blocks between the switch and the fire spinner, if the spinner is above keen; ten blocks between the switch and the spinner if placed horizontally, and 12 blocks if the fire spinner is below keen--you get the point, right? The spinner must be out of sight when the switch is flipped. Alternately, you can use a combination of a slider switch and a button switch--both linked to the fire spinner--then the spinner can be in plain view. All the fire spinners in the whole level must be aiming in the exact same direction for either of these tricks to work.
Try this: Place a full key-gem holder in your level, and link it to a door. Now link a button switch to the key-gem holder. When you press the button, the key-gem holder empties. OMG!
Sure, keen can walk on air, but not without the help of foreground tile number $03FC (located directly above the blue Tart Stix in the foreground block selection), keen would plummet. Don't be mean: give the player some kind of a clue where the invisible floor ends.
Levels that are 16 blocks tall will shake; this could be useful for an earthquake scenario. Take the "BLOCK" tiles out of the border or else you'll see them in the game.
There is nothing like designing complex combinations of info-layer arrow paths for volte-faces and platforms. Arrow directions can be reversed using a slider-switch. Keep in mind that the route must describe a complete circuit at all times, or be terminated by an arrow pointing in the exact opposite direction as the one preceding it. Oh the joys of totally confusing players!
Using a clever combination of "B" tiles and switches, you can move the location slicestars bounce. Slicestars look for "B" info tiles just like falling platforms. Without "B" tiles, a slicestar travels up or right (depending on which kind it is), till it reaches a solid foreground block; at which point it embeds itself in the wall--not a pretty site to be sure!
Using a slider switch to turn off a "B" tile will result in an identical tragedy, unless there
is another "B" tile located farther on. By turning off a "B" tile, allowing the slicestar to pass that location, then turning it back on, the player can effectively change the location the slicestar bounces, opening up otherwise impossible to reach places in the level.
(Thanks to James aka Dr. Witherstone for finding most of these bugs)