DNA copying challenge (#1031)

A challenge that utilizes a stack.
Closes #932.

Demo:
```
scripts/play.sh --scenario data/scenarios/Challenges/dna.yaml --autoplay
```
![Screenshot from 2024-10-13 17-06-06](https://github.com/user-attachments/assets/678984b0-f83d-4e0d-8958-dfcd33461ce6)

data/scenarios/Challenges/00-ORDER.txt

@@ -16,6 +16,7 @@ wave.yaml
 gallery.yaml
 wolf-goat-cabbage.yaml
 blender.yaml
+dna.yaml
 friend.yaml
 pack-tetrominoes.yaml
 dimsum.yaml

data/scenarios/Challenges/_dna/lab.sw

@@ -0,0 +1,177 @@
+def doN = \n. \f. if (n > 0) {f; doN (n - 1) f} {}; end;
+
+def getBaseForNumber = \n.
+    if (n == 0) {
+        "guanine";
+    } {
+        if (n == 1) {
+            "cytosine";
+        } {
+            if (n == 2) {
+                "adenine";
+            } {
+                "thymine";
+            };
+        };
+    };
+    end;
+
+def getNumberForBase = \n.
+    if (n == "guanine") {
+        0;
+    } {
+        if (n == "cytosine") {
+            1;
+        } {
+            if (n == "adenine") {
+                2;
+            } {
+                3;
+            };
+        };
+    };
+    end;
+
+/** Toggle the lowest bit */
+def getComplementNumber = \n.
+    if (n == 0) {
+        1;
+    } {
+        if (n == 1) {
+            0;
+        } {
+            if (n == 2) {
+                3;
+            } {
+                2;
+            };
+        };
+    };
+    end;
+
+def waitUntilSomethingExists =
+    maybeItemHere <- scan down;
+    case maybeItemHere (\_. 
+        watch down;
+        wait 1000;
+        waitUntilSomethingExists;
+    ) return;
+    end;
+
+def waitUntilHere = \item.
+    hereNow <- ishere item;
+    if hereNow {} {
+        watch down;
+        wait 1000;
+        waitUntilHere item;
+    };
+    end;
+
+def waitUntilOccupied =
+    stillEmpty <- isempty;
+    if stillEmpty {
+        watch down;
+        wait 1000;
+        waitUntilOccupied;
+    } {};
+    end;
+
+def myStandby = \receptacleLoc.
+    teleport self receptacleLoc;
+    entToClone <- grab;
+    teleport self (36, -11);
+    turn back;
+    return $ inR entToClone;
+    end;
+
+def placeBase = \standbyFunc. \n. 
+
+    if (n > 0) {
+        idx <- random 4;
+        let entTemp = getBaseForNumber idx in
+        let ent = entTemp in
+        create ent;
+        place ent;
+        move;
+
+        clonedOrganism <- placeBase standbyFunc $ n - 1;
+
+        // Unwinds the stack; verifies the original placement order
+        placedEnt <- instant waitUntilSomethingExists;
+        let isGood = ent == placedEnt in
+        move;
+
+        if isGood {
+            return clonedOrganism;
+        } {
+            return $ inL ();
+        }
+    } {
+        // Returns the clonedOrganism
+        standbyFunc;
+    };
+    end;
+
+def makeDnaStrand = \receptacleLoc.
+    teleport self (5, -2);
+
+    dims <- floorplan "DNA decoder";
+    let decoderWidth = fst dims in
+    eitherClonedOrganism <- placeBase (myStandby receptacleLoc) decoderWidth;
+
+    case eitherClonedOrganism (\_.
+        create "pixel (R)";
+    ) (\clonedItem.
+        instant $ (
+            teleport self (0, -11);
+            waitUntilHere "switch (on)";
+
+            bottomWaypointQuery <- waypoint "receiver" 1;
+            let receptacleLoc2 = snd bottomWaypointQuery in
+            teleport self receptacleLoc2;
+
+            sow clonedItem;
+            create clonedItem;
+            k <- robotnamed "keeper";
+            give k clonedItem;
+
+            let slideBox = "slide box" in
+            create slideBox;
+            give base slideBox;
+            say $ "You got a new \"" ++ slideBox ++ "\"";
+        );
+    );
+    end;
+
+def waitForCloneableOrganism =
+
+    waypointQuery <- waypoint "receiver" 0;
+    let receptacleLoc = snd waypointQuery in
+    organism <- instant (
+        teleport self receptacleLoc;
+
+        waitUntilOccupied;
+
+        thingHere <- scan down;
+        case thingHere (\x. return $ inL x) (\item.
+            isOrganism <- hastag item "organism";
+            return $ inR item;
+        );
+    );
+
+    case organism (\_.
+        say "Not a cloneable organism!";
+        waitForCloneableOrganism;
+    ) (\item.
+        create "pixel (G)";
+        makeDnaStrand receptacleLoc;
+    );
+    end;
+
+def go =
+    waitForCloneableOrganism;
+    turn east;
+    go;
+    end;
+
+go;

data/scenarios/Challenges/_dna/mirrorbot.sw

@@ -0,0 +1,99 @@
+def doN = \n. \f. if (n > 0) {f; doN (n - 1) f} {}; end;
+
+def getBaseForNumber = \n.
+    if (n == 0) {
+        "guanine";
+    } {
+        if (n == 1) {
+            "cytosine";
+        } {
+            if (n == 2) {
+                "adenine";
+            } {
+                "thymine";
+            };
+        };
+    };
+    end;
+
+def getNumberForBase = \n.
+    if (n == "guanine") {
+        0;
+    } {
+        if (n == "cytosine") {
+            1;
+        } {
+            if (n == "adenine") {
+                2;
+            } {
+                if (n == "thymine") {
+                    3;
+                } {-1};
+            };
+        };
+    };
+    end;
+
+/** Toggle the lowest bit */
+def getComplementNumber = \n.
+    if (n == 0) {
+        1;
+    } {
+        if (n == 1) {
+            0;
+        } {
+            if (n == 2) {
+                3;
+            } {
+                2;
+            };
+        };
+    };
+    end;
+
+def placeComplementOf = \item.
+    let baseNumber = getNumberForBase item in
+    if (baseNumber >= 0) {
+        let complementNumber = getComplementNumber baseNumber in
+        let newItem = getBaseForNumber complementNumber in
+        move;
+        create newItem;
+        place newItem;
+    } {
+        let sludge = "organic sludge" in
+        create sludge;
+        place sludge;
+    }
+    end;
+
+def waitUntilHere =
+    watch down;
+    wait 1000;
+
+    maybeItemDown <- scan down;
+    case maybeItemDown (\_. waitUntilHere) (\itemHere.
+        placeComplementOf itemHere;
+    );
+    end;
+
+def waitUntilEmpty =
+    watch down;
+    wait 1000;
+    emptyHere <- isempty;
+    if emptyHere {
+        // reset the position
+        turn back;
+        move;
+        turn back;
+    } {
+        waitUntilEmpty;
+    }
+    end;
+
+def go =
+    instant waitUntilHere;
+    waitUntilEmpty;
+    go;
+    end;
+
+go;

data/scenarios/Challenges/_dna/resetter.sw

@@ -0,0 +1,48 @@
+def doN = \n. \f. if (n > 0) {f; doN (n - 1) f} {}; end;
+
+/**
+Assumes we are on the left edge of a row of nucleobases
+*/
+def resetPlayfieldRow =
+    dims <- floorplan "DNA decoder";
+    let decoderWidth = fst dims in
+    doN decoderWidth (grab; move;);
+    end;
+
+def resetPlayfield =
+    teleport self (5, -2);
+    resetPlayfieldRow;
+    teleport self (5, -3);
+    resetPlayfieldRow;
+
+    teleport self (5, -11);
+    resetPlayfieldRow;
+    teleport self (5, -12);
+    resetPlayfieldRow;
+    end;
+
+def watchSwitch = \lastState.
+    watch down;
+    wait 1000;
+    found <- scan down;
+    case found return (\item.
+        if (item != lastState) {
+            if (item == "switch (off)") {
+                loc <- whereami;
+                resetPlayfield;
+                teleport self loc;
+            } {
+            };
+        } {};
+        watchSwitch item;
+    );
+    end;
+
+def go =
+    instant $ (
+        found <- scan down;
+        case found return watchSwitch;
+    );
+    end;
+
+go;