The Movement Pipeline

The Two-Pass Movement Algorithm

The Movement Pipeline

Questions

How do movement-changing spell effects interact with each other?

Moonwalks

Why is it called a moonwalk?

Why do moonwalks happen?

Show me an easy diagram of a moonwalk!

How can I create a moonwalk in general?

The Flying Leap Deck

The Two-Pass Movement Algorithm. Sanctum uses a two-pass movement algorithm.

1. Overstacking. In pass I, all groups “move” without regard to the normal stacking limit of 1 group per square. Each square can have any number of groups, friendly or enemy. This pass is not animated, so you can't see it.
2. Unstacking (overstack resolution). In pass II, all groups in a square “vote” for exactly 1 winner. That group “wins” the square. All other groups join it if they can, or bounce back if they can't. Each group animates its result. This pass is what you've always seen.

At the end of movement execution, the stacking limit is restored for all squares.

The Movement Pipeline. Pass I is applied to all groups, in player initiative sequence, as follows:

• For the initiative player:
  • All of its player-controlled groups; then
  • All of its computer-controlled groups.
• For the non-initiative player:
  • All of its player-controlled groups; then
  • All of its computer-controlled groups.
• For the neutral player:
  • Bot stop: All of its player-controlled groups remain stationary.
  • All of its computer-controlled groups.

Pass II is then checked for all squares on the board.

Questions

How do movement-changing spell effects interact with each other? The key concept is: Movement orders can be overwritten, but this happens in a specific sequence. The last movement order assigned to a group “wins”, and that's how the group will move.

Moonwalks

Why is it called a moonwalk? The group doesn't change its facing prior to moonwalking, so it may appear to move sideways on the board, or even backward.

Why do moonwalks happen? Step (II.c) of the Movement Pipeline is a deliberately simplified explanation. In reality, the “voting” is done between only two groups at a time. A square with N groups actually votes N -  1 times. These votes are interleaved with all the other squares, in parallel. Thus, if square A has 4 groups and square B has 1 group, then square B will finish its “voting” before 2 of the groups in square A have even been considered!

Show me an easy diagram of a moonwalk! Here's a simple diagram for one specific moonwalk solution. Group A will moonwalk.

• D up. First, order group D with 5 recruits “upward” (into A's square).
• A left. Second, order group A with 4 recruits “leftward” (into B's square).
• C up. Third, order group C with 5 recruits “upward” (into B's square).
• B stand. Have group B, with 1 recruit, stand still.

How can I create a moonwalk in general? Here, we give a more verbose description for the general solution. First, some nomenclature:

• Upper-case letters A, B, C, D are groups.
• Lower-case letters a, b, c, d are squares.
• + denotes two groups joining.
• > compares two groups' sizes.

To force group A in square a to moonwalk, do this:

• Have group B in b next to a.
• Have group C in c next to b.
• Have group D in d next to a.

Requirements:

9. A+B looks like a legal joining, and C+B looks legal. (In the above example, A+B = 5, and C+B = 6.)
   This is what allows you to order both A and C to move into b.
10. C is “faster than” A. Simplest method: C > A. (In the above example, C = 5 and A = 4.)
    This creates the race condition that puts A into “limbo”, giving D time to sneak in behind it and steal its square away.
11. A+B+C isn't legal.
    This is what makes A bounce back. (In the above example, A+B+C = 10, which violates the maximum group size.)
12. A+D isn't legal.
    Simplest method: A+D > 8. Or, Ostracize D. This is what forces A to moonwalk. (In the above example, A+D = 9.)

Assign the following movement orders, in exactly this sequence:

1. D to a.
2. A to b.
3. C to b.
4. (Have B stand still in b.)

Here's how it will execute.

• (I.b) Overstack.
  • D can move to a.
  • A can move to b, and A+B looks legal.
  • C can move to b, and C+B looks legal.
  • Now D is alone in a, and A, B, C are overstacked in b.
• (II.c) Voting.
  • D is alone in a. D “wins”, and now owns a. (This is why you issue D's movement order before A's.)
  • 3 groups vie for square b. Unstacking processes 2 groups at a time. (This is why you use 3 groups.)
  • A group that didn't move is automatically fastest. That's B.
  • C is faster than A, by construction in (j). So C is the second-fastest group.
• (II.d) Unstacking.
  • B and C are chosen, in that order. B+C looks legal, by (i). So they join.
  • Now BC + A is checked. It is not a legal joining, by (k).
  • A bounces back to a.
• (II.e) Moonwalking.
  • D already owns a, from step (iii).
  • D+A is not a legal joining, by (l).
  • A moonwalks.

The Flying Leap Deck. This deck demonstrates the spectacular effect of a controlled moonwalk. It is not recommended that you try this deck in ranked play, due to the sheer difficulty of its winning combination.

1. Play in Badlands (so that there are no forest squares).
2. Cast a forest at f, diagonally adjacent to enemy Sanctum.
3. Cast two forests at A and B.
4. Terrain-Bind group A (into forest).
5. If your opponent inconveniently creates any other forest squares, you'll have to change their terrain to something else.
6. Force group A to moonwalk, as described above.

Group A must moonwalk. Corollary: It must be the case that A can't legally enter either squares A or B (which is why it's moonwalking). Because of the Terrain-Bind, the only other square on the board that group A can legally enter is f. Hence, A leaps directly to f.

7. Somehow ensure that your opponent has no novices left in her Sanctum.
8. Cast Lienna's Steed for the win. (Or, make group A big enough, and just fight your way in.)

v2.20.00 Last updated 2009/03/21