Platforming games with one-way platforms

[thefox]

I was thinking about adding support for one-way platforms to my engine. I guess platforms that only allow moving up through them are the most common case. Can you name games that have horizontal one-way platforms (ones that only allow movement to left or right), or games with platforms that only allow movement down?

I'm mainly interested in finding out how such platforms (may) have been utilized in gameplay.

[Sik]

I can't think of any in particular right now, but such platforms would be used to make one-way paths (e.g. a solid from bottom platform would be used to block a passage you fall into, preventing you from trying to go back upwards - especially useful for secret paths).

[tepples]

Yoshi's Island has those pinball flipper things that allow only downward movement, and it's got plenty of puzzles based on upward-only platforms. And I think Sonic games have plenty of one-way doors that allow movement only leftward or rightward. Was it Chemical Plant Zone in Sonic 2?

[tokumaru]

I don't think you're going to find many examples of 1-way walls, because visually, that doesn't make much sense. It barely makes sense with floors (why can't a character jump down the same way he used to jump up?).

[thefox]

I can't think of any in particular right now, but such platforms would be used to make one-way paths (e.g. a solid from bottom platform would be used to block a passage you fall into, preventing you from trying to go back upwards - especially useful for secret paths).

Yeah I'd expect it to be mostly used for puzzley stuff, if any.

And I think Sonic games have plenty of one-way doors that allow movement only leftward or rightward. Was it Chemical Plant Zone in Sonic 2?

Watched some footage on YouTube, but not sure which ones you were referring to.

I don't think you're going to find many examples of 1-way walls, because visually, that doesn't make much sense. It barely makes sense with floors (why can't a character jump down the same way he used to jump up?).

Yeah, personally I couldn't think of any, that's why I made the topic. I agree about the visuals, but the graphics could also be very explicitly "one way" (like arrows) so that it could be used as a puzzle element.

About floors, some games (like Contra) also have support for dropping down from such platforms. In that case the visuals would make sense at least (although I don't think it's much of a problem with floors if they don't).

[tepples]

Makes perfect sense to me.

onewayfloor.gif (8.25 KiB) Viewed 3322 times

[darryl.revok]

I know I've seen this but I'm having trouble coming up with too many examples.

Metal Storm has floors that you can only jump through in one direction.

If I remember correctly, this little windows game we had at school called Chip's Challenge had floors like you described from a top down view.

[mikejmoffitt]

I think the implication is that the platform is slightly further back in the Z dimension, which is often only hinted at through shadows, darkening, or an oblique view. That falls apart when the player is unable to drop back down, though. It works in a game like Kirby's Adventure, which handles both situations, while it makes less sense in Super Mario World.

Indeed, Chip's Challenge had floors with arrows painted on them. It is hard to justify in the "how does this thing work in the world it is in?" sense, but it is fine in a game which already features abstract ideas or characters, domain-specific rules of physics and behavior that the player accepts simply by playing the game.

[darryl.revok]

I really feel like there are a lot more examples but most of them are for top-down games

I recall areas in Seiken Densetsu III where wind is blowing really hard in one direction preventing you from walking against it. You have to flip switches to change the angles of the wind generators.

If you can switch direction, they almost function like a door in a gameplay sense. You get to a location, it forces you toward a certain path, you get to the end of that path and there's a switch, return and you can pass through to the next area, but then you couldn't go back the same way.

[tokumaru]

And I think Sonic games have plenty of one-way doors that allow movement only leftward or rightward. Was it Chemical Plant Zone in Sonic 2?

I immediately thought of Chemical Plant Zone too, but even though it has a lot of intersecting paths with ramps and loops, I don't think it has actual 1-way walls. There are doors that closes as soon as you go through them, but that's a living object, not part of the scenery. I don't think you'll find any examples without visual cues that something changed to make the wall solid once the player went through it.

I agree about the visuals, but the graphics could also be very explicitly "one way" (like arrows) so that it could be used as a puzzle element.

Yeah, that would be a good use for such blocks, but I can't think of any games that did this with walls.

[tepples]

And I think Sonic games have plenty of one-way doors that allow movement only leftward or rightward. Was it Chemical Plant Zone in Sonic 2?

I immediately thought of Chemical Plant Zone too, but even though it has a lot of intersecting paths with ramps and loops, I don't think it has actual 1-way walls. There are doors that closes as soon as you go through them, but that's a living object, not part of the scenery.

Implementation and terminology detail. Are rings in that game a "living object"? Are ? blocks that can be bumped from below in Super Mario Bros. a "living object"?

[Drew Sebastino]

Whenever I think of an object, I think of a sprite, whereas with something that isn't, I think of the background. However, this line can be blurred, like in Super Mario World, cant coins be either part of the background or a sprite? You know, how do the Super Mario Bros games handle "BG objects?" I imagine it works just like BG collisions, but it each spot in the BG collision map can have more than just "solid" and "empty", as if you hit a question mark block, it would run the code for a solid object, (jumping to either the code for a regular solid area or running a copy,) but would also spawn an object, being a power up, and would change the BG map so that you cannot just hit block and have something come out more than once, if any of what I said makes sense. Does anyone know if this is tied to the tilemap in SMW, or if this is a separate table?

[psycopathicteen]

I think they're all tied to the tile map. Each block probably has a routine that is triggered whenever Mario hits it, as well as typical collision data. Flying blocks are always objects though.

[tokumaru]

Implementation and terminology detail.

A wall is dumb. It may have attributes specifying how the objects interact with it, but it doesn't do anything. A door, on the other hand, is an active object, it opens and it closes, depending on the decisions made by its AI routine. These "smart" objects have hardly anything to do with how engines implement platforms.

Are rings in that game a "living object"?

I think so.

Are ? blocks that can be bumped from below in Super Mario Bros. a "living object"?

I'm not very familiar with the SMB engine, but I guess it would make sense to have them be part of the scenery until they're hit from below, when a "living object" would be instantiated to handle the interaction with the player.

Whenever I think of an object, I think of a sprite, whereas with something that isn't, I think of the background.

This way of thinking is more suited to 16-bit consoles and newer, where sprites are abundant, or to older NES games that were made before games were expected to have large quantities of big interactive objects. In order to remain competitive, many 8-bit games started using the background to permanently or temporarily (in case they could be moved/destroyed) represent interactive objects.

In my platform engine I have an object system that constantly monitors the new columns and rows that are being drawn for scrolling and tests for intersections between these columns/rows and background objects, superimposing the objects' tiles whenever necessary, so they're automatically drawn along with the background even though they're not part of the level map (they're regular spawned objects). This is great for making destructible objects, patching blocks so they look different from other instances of the same blocks, or simply not polluting the level map with things that are not part of the scenery.

[tepples]

Are ? blocks that can be bumped from below in Super Mario Bros. a "living object"?

I'm not very familiar with the SMB engine, but I guess it would make sense to have them be part of the scenery until they're hit from below, when a "living object" would be instantiated to handle the interaction with the player.

Likewise, a one-way wall would be scenery until the player touches it from the correct side, at which time it spawns a "living object" to handle the open and close animation, whether rendered as sprites or as background changes.