Level 01, "I clicked a Lem; I liked it!": Destructive skills tank on steel, constructive skills turn around when building into terrain.
Level 02, "I love Rock 'n Roll": one lemming will always slip past a stacker at release rate 1 or higher (with a single hatch)
Level 03, "Into the pits": Basher- and Digger pits to contain lemmings
Level 04, "Going under": It is more efficient to go through larger chunks of terrain in one piece than to waste destructive skills on single smaller obstacles.
Level 05, "Over the rainbow": turning around Miners and Builders with Blockers
Level 06, "Ordinary world":1-of-everything level
Level 07, "Pick me up before you go-go": pickup skills, pre-placed lemmings
Level 08, "Glide and joy": to turn around a lemming on an even steel surface, you can build, then dig, then build into the remnants of the first staircase
Level 09, "Grenade": use release-rate increase to get past triggered traps
Level 10, "Noel nouvelet": 1-of-everything level with NeoLemmix skills
Level 11, "Can't stop this thing we started": build across Digger shafts to force lemmings to fall through facing in one direction only (=Dolly-Dimple trick)
Level 12, "We're not gonna take it": cut off a Builder's staircase behind him to isolate him as a pioneer
Level 13, "Paranoid": horizontal one-way arrows can be dug into, but vertical one-way arrows can't be bashed through
Level 14, "Digital world": exit buttons; digging to create a Climber path
Level 15, "Octopus's garden": introduce the Disarmer, and the fact that Strato likes animal traps!
Level 16, "Jump!": six-pixel jumps
Level 17, "How to save a life": using Stoners as stepping-stones for Builders; getting a second pioneer lemming by trapping the crowd at the foot of a wall and then having one lemming glide over whatever is holding the others back
Level 18, "Stop and stair": three-builder wall, sealing off Basher tunnels with Builders (reverse logic of level 12)
Level 19, "Lemming, I hardly knew ya!": It is possible to fall and climb through Blockers; this allows you to free them with Diggers.
Level 20, "Flight of the bumblebee": the flying-Builder trick (building in mid-air before the Digger falls down)
Level 21, "Rainbow in the dark": cancel one Miner with a Miner into the opposite direction
Level 22, "Locked away": Climbers can be contained by putting constructive skills at the top of straight walls
Level 23, "Shatter me": assigning Floaters and Gliders early or late to influence their speed
Level 24, "Hells bells": making Miners continue with Builders
Level 25, "Bash to you": Bashers can move down slopes
Level 26, "Don't stop me now": cancel one Digger with a Digger looking in the opposite direction --> re-use the Dolly-Dimple trick from Level 11 at the end!
Level 27, "Don't bring me down": You can move Bashers down (see level 25) by digging under them while they are bashing.
Level 28, "Bashing through the snow": cancelling Bashers mid-swipe with Walkers and Builders
Level 29, "Behind blue eyes": isolating a pioneer lemming from behind the crowd instead of from the front
Level 30, "In the army now": using terrain to turn lemmings around before destroying it to let them through in the opposite direction (adaptation of the Dolly-Dimple logic)
Level 31, "The one that go away": using lemmings slipping past Stackers to your advantage
Level 32, "Where them Lems at": using Basher tunnels in creation to turn lemmings around that couldn't turn around anymore once the tunnel is completed
Level 33, "Mein kleiner grüner Kaktus": using Blockers to cancel Diggers that only dig on the edge and don't have terrain right beneath them
Level 34, "Takes two to tango": the double-Builder turnaround (having two Lemmings build right next to each other will cause the one on the front to bump against the staircase of the Builder behind him and turn around)
Level 35, "While my Lemming gently builds": applying the logic from level 32 to use a Builder staircase in-creation to get a lemming across a water pond; once the Builder is finished, this path is closed off completely
Level 36, "Pull me under": putting a Blocker on a staircase to later free him with a Basher
Level 37, "Running up that hill": Bashers can also slope up (see level 25) when facing towards indestructible terrain at a low angle
Level 38, "Rock, Paper, Scissors": Stackers can be used to fill the space between a Stoner's hands and feet, thereby creating a straight wall of 6 pixels in height, which the Lemmings can jump (see level 16) over
Level 39, "Vegas Lights": Stoners can be used to make Swimmers dive
Level 40, "Absolute beginners": Many newbie solutions involve excessive use of Blockers and/or Builders - start looking for approaches without either of them (only for the talisman)!