Just another idea I thought of.  This is an 'instant' skill in the same category as Walker, Cloner and Jumper.

When assigned, the Lemming accelerates straight upwards with a flame jet coming from their feet (or a jetpack).  They continue until they hit their head on an obstruction or die by hitting a trap or the deadly ceiling.

Some thoughts on the mechanics and their uses:

* If the lemming is assigned a Shimmier just before they hit their head, they will latch on and attempt to shimmy across the ceiling.
* The lemming cannot be interrupted while rocketing skywards (even with a Walker), although they can be sacrificed in their current position with a Bomber or Stoner.
* A Rocketer will explode instantly when given a Bomber or when the countdown reaches 0 with the nuke.
* Cloning a Rocketer will create a 2nd Rocketer facing the other direction.
* Gliders and Floaters can be assigned the skill, and will fly straight up from their current position.  After hitting their head, they will resume gliding or floating, whichever is applicable.
* Drowners can be assigned the skill and will save them from death (assuming they don't hit their head and fall straight back in the drink).
* Swimmers can be assigned the skill.
* Fallers can be assigned the skill.
* Jumpers can be assigned the skill.
* Blockers cannot be assigned the skill.
* Climbers cannot be assigned the skill.
* Lemmings performing constructive (e.g. Builder) or destructive tasks (e.g. Basher) can be assigned the skill and will stop their current task to become a Rocketer.

By itself, the skill can be used to delay a lemming but otherwise doesn't do much else.  The skill's main use would be its synergy with other tasks, like reaching very high ceilings with a Shimmier, a degree of flight control with a Glider, or attempting to land on a Builder or Platformer's bridge above them while it is being built.  As one example, if you need to traverse a stretch of water with a relatively low ceiling and don't have a Swimmer available, it can be traversed with a Glider and one or two Rocketers.

If the dead vertical direction is too restrictive, then it could be slightly changed to be a very sharp angle instead, so there is a small element of horizontal motion so they can land on high ledges (e.g. 4 pixels up for every 1 pixel across).  Hitting a wall would act the same way as hitting the roof (not sure if the should instantly start climbing if they're a Climber).

So, this is essentially the introduction of the L2 Jetpack. Or the Ballooner.

The transition to a Shimmier is what seems most interesting to me here. Neither the Ballooner can do this (because the balloon pops before the lemming himself even gets close to the ceiling), nor the Jetpack.

I don't get though why it shouldn't be possible to assign a Rocketeer (shouldn't it be double-ee? ) to a Climber? He's already in the perfect position for it, and this would allow the Climber to easily continue if the wall stops somewhere.

Blockers of course shouldn't be able to be assigned Rocketeers, since it's impossible to assign anything else than a Walker, permanent or lethal skills to a Blocker.

The "low ceiling above water" example seems quite fiddly for a combination of Glider and Rocketeer, though. A single Shimmier would probably be the easiest solution for this specific example (since you established you don't have a Swimmer in this scenario).

In general, most of the criticism that applies to the Ballooner also applies to this: We already have Gliders with updrafts to allow lemmings to move upwards without any solid terrain to latch onto.

When it comes to going straight upwards through solid terrain - i.e. upward Digging, as Proxima suggested - then I'm all in!

I like this idea.

Something to note: the "Reacher" phase of the Shimmier is able to jump through a 2px platform and then land on it. So... I'm thinking the Rocketer should be able to do the same, and therefore be able to jump through Platformer bridges and other platforms up to 2px thick.

Hi again, question to WillLem, how exactly does this work?

Something to note: the "Reacher" phase of the Shimmier is able to jump through a 2px platform and then land on it.

I tried to use this behaviour for a puzzle, i.e. having a Shimmier jump through a Platformer's bridge (which is only 1 pixel thick), but it doesn't work. Obviously, the Shimmier's main purpose is holding on to a platform.

Did you mean 2 pixels in length? I tried that as well, i.e. cancelled the Platformer with a Miner after two pixels - the Reacher still doesn't jump through it.

Could you maybe elaborate on what exactly you meant here?

This suggestion has been closed (as a rejected suggestion) as per the results of the poll in the "Final New Skill" topic: https://www.lemmingsforums.net/index.php?topic=4686.0