Previous contest design rules

[Proxima]

We've had so many contests now, it's about time someone compiled a list of all the rules that have been thought up. This may be inspiration for anyone thinking of rules for future contests. Of course, it's okay to repeat a rule from an old contest -- that will give people who missed out on the old contest another chance to come up with something.

There were three unofficial contests, before the numbered official contests started. Lemmix was used for these, so the first contest refers to the original 8 skills.

1 - Make a level with one of each skill
2 - Make a level in the crystal style with no builders
3 - Make a level with 5 or fewer lemmings

The first eight official contests only had a single rule each:

1 - Make a level using an unofficial tileset
2 - Make a Fun/Tame level
3 - Tag Team (one person designs the terrain, the other places objects and assigns stats)
4 - Make a level with exactly 5 total skills
5 - Make a level with a save requirement at most 10%
6 - Make a level with no constructive skills
7 - Make a level with at least 4 exits
8 - Make a level with a L2 or L3 style

Contest #9 was the abortive "here are three rules, try to loophole one of them", which attracted no entries, but led to the three-rule format followed by all subsequent contests. (Note that this contest was ignored in the numbering, so the next contest is also numberered 9.) An asterisk before a rule indicates a repeat or near-repeat of a rule from an earlier contest.

Rules from the "loophole" contest:
R1 - Make a level with at most 12 (terrain pieces + objects), with at most 4 being objects
R2 - Make a level where all terrain is steel that requires at least two destructive skills to solve
R3 - Make a level using exactly the terrain + objects of an original Lemmings level

9R1 - Make a level with only new skills
9R2 - Make a level with only one lemming
9R3 - Make a level with exactly two types of skill
10R1 - Make a level with no permanent skills
*10R2 - Make a Fun/Tame level
10R3 - Make a level with at least two new object types
11R1 - Make a level with save 2/2, at most 1 of each permanent skill
11R2 - Make a level with 1 of each provided skill
*11R3 - Make a level with no constructive skills
12R1 - Make a level with a time limit of 1min or less
12R2 - Make a level with no destructive skills
12R3 - Make a VGASPEC level
13R1 - Make a level with tileset mixing
13R2 - Make a level with at least two intended solutions
*13R3 - Make a level without using any official tilesets
14R1 - Make a level with 3 hatches and 3 lemmings
14R2 - Make a level with no steel and 2 hatches
14R3 - Make a level with exactly 2 of any 8 skills
15R1 - Make two levels with the same terrain, but one is flipped
15R2 - Make a minimal-size level with at most 10 lemmings
*15R3 - Make a level with only new skills
16R1 - Make a level with height at least 3 times its width
16R2 - Make a level with at most 2 minutes and hatch-exit distance at least 2 screens
16R3 - Make a level with at least 3 hatches, save requirement (h-1)/h * 100%
17R1 - Make a level using only tilesets you haven't used before
17R2 - Make a level with exactly 1 type of skill from each category
17R3 - Make a level with only one type of terrain piece
18R1 - Make a level with one hatch, one exit and no other objects
18R2 - Make a subset of an official level
*18R3 - Make a level with at most two types of skill
19R1 - Make a level with at most 3 non-permanent skills
19R2 - Make a level whose terrain spells your username
19R3 - Make a level with exactly 1 lemming and save requirement at least 2
20R1 - Make a level with horizontally and vertically symmetrical terrain
20R2 - Make a level with at least 10 skill types, at most 5 of each
20R3 - Make a fake "disjoint union"
21R1 - Make a level using at least 3 jumpers
21R2 - Make a level with one hatch, at least two exits, and each exit must be limited to an equal share of the save requirement
21R3 - Make a level depicting a recognisable character, object or landmark
22R1 - Make a level using only original skills and objects
22R2 - Make a level using only new skills and objects
22R3 - Make a level with at least one neutral and at least one zombie
23R1 - Make an X-of-everything level for X at most 10
*23R2 - Make a minimal-size level with at most 10 lemmings
23R3 - Make a level divided into two sections, one tileset in each
24R1 - Make a level with exactly one new skill type
24R2 - Make a level at least 200,000 pixels large
24R3 - Make a level with a rule from a previous contest
25R1 - Make a level with only preplaced lemmings, and no two having the same permanent skills
25R2 - Make a level with at most 10 terrain pieces and at most 10 objects
25R3 - Make a level that depicts a physical object
26R1 - Make a level with no destructible terrain
26R2 - Make a level with infinitely many jumpers
26R3 - Make a level with only L2 tilesets and L2 skills
27R1 - Make a level with only constructive skills and bombers
27R2 - Make a level in which all lemmings are pre-assigned swimmers (in NL) or runners (in Lix)
27R3 - Make a level with RR 99 and at most 10 lemmings
28R1 - Make a level with an entrance near each corner and the exit in the centre
28R2 - Make a level depicting an animal
*28R3 - Make a minimal-size level with at most 9 lemmings and at most 9 skills
29R1 - Make a level with three hatches on one side and the exit on the other
29R2 - Make a level depicting a vehicle
29R3 - Make a level with at least three linked teleporters (in NL) or flingers (in Lix)
*30R1 - Make a level using a single tileset you haven't used before
30R2 - Make a level with only destructive skills
30R3 - Make a level in the l2_classic style using only the classic 8 skills and classic objects

[mobius]

Good idea to list them all. I had forgotten most of them; and totally forgot some which I wasn't around at the time for. I think it's also alright to repeat a rule once and a while;  Some are more fun than others.

[namida]

I would suggest that each contest should have at least one entirely new rule, but I don't see a problem with repeating as long as some new ones are in the mix too. (And just to be clear, this itself isn't a rule for the contest rules or anything - just my opinion on the subject.)

[Crane]

A slightly moot point, but "*18R3 - Make a level with at most two types of skill" is not quite the same as "9R3 - Make a level with exactly two types of skill" since you were allowed only one skill in the 18R3 ruleset.