diff --git a/royale.go b/royale.go
new file mode 100644
index 0000000..3ba97fd
--- /dev/null
+++ b/royale.go
@@ -0,0 +1,82 @@
+package rules
+
+import (
+	"errors"
+)
+
+type RoyaleRuleset struct {
+	StandardRuleset
+
+	Turn              int32
+	ShrinkEveryNTurns int32
+
+	// Output
+	OutOfBounds []Point
+}
+
+func (r *RoyaleRuleset) CreateNextBoardState(prevState *BoardState, moves []SnakeMove) (*BoardState, error) {
+	if r.ShrinkEveryNTurns < 1 {
+		return nil, errors.New("royale game must shrink at least every 1 turn")
+	}
+
+	nextBoardState, err := r.StandardRuleset.CreateNextBoardState(prevState, moves)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: LOG?
+	err = r.populateOutOfBounds(nextBoardState)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: LOG?
+	err = r.eliminateOutOfBounds(nextBoardState)
+	if err != nil {
+		return nil, err
+	}
+
+	return nextBoardState, nil
+}
+
+func (r *RoyaleRuleset) populateOutOfBounds(b *BoardState) error {
+	r.OutOfBounds = []Point{}
+
+	if r.ShrinkEveryNTurns < 1 {
+		return errors.New("royale game must shrink at least every 1 turn")
+	}
+
+	if r.Turn < r.ShrinkEveryNTurns {
+		return nil
+	}
+
+	numShrinks := r.Turn / r.ShrinkEveryNTurns
+	minX, maxX := numShrinks, b.Width-1-numShrinks
+	minY, maxY := numShrinks, b.Height-1-numShrinks
+	for x := int32(0); x < b.Width; x++ {
+		for y := int32(0); y < b.Height; y++ {
+			if x < minX || x > maxX || y < minY || y > maxY {
+				r.OutOfBounds = append(r.OutOfBounds, Point{x, y})
+			}
+		}
+	}
+
+	return nil
+}
+
+func (r *RoyaleRuleset) eliminateOutOfBounds(b *BoardState) error {
+	for i := 0; i < len(b.Snakes); i++ {
+		snake := &b.Snakes[i]
+		if snake.EliminatedCause == NotEliminated {
+			head := snake.Body[0]
+			for _, p := range r.OutOfBounds {
+				if head == p {
+					// Snake is now out of bounds, eliminate it
+					snake.EliminatedCause = EliminatedByOutOfBounds
+				}
+			}
+		}
+	}
+
+	return nil
+}
diff --git a/royale_test.go b/royale_test.go
new file mode 100644
index 0000000..178d042
--- /dev/null
+++ b/royale_test.go
@@ -0,0 +1,141 @@
+package rules
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRoyaleRulesetInterface(t *testing.T) {
+	var _ Ruleset = (*RoyaleRuleset)(nil)
+}
+
+func TestRoyaleDefaultSanity(t *testing.T) {
+	boardState := &BoardState{}
+	r := RoyaleRuleset{}
+	_, err := r.CreateNextBoardState(boardState, []SnakeMove{})
+	require.Error(t, err)
+	require.Equal(t, err, errors.New("royale game must shrink at least every 1 turn"))
+
+	r = RoyaleRuleset{ShrinkEveryNTurns: 1}
+	_, err = r.CreateNextBoardState(boardState, []SnakeMove{})
+	require.NoError(t, err)
+}
+
+func TestRoyalePopulateObstacles(t *testing.T) {
+	tests := []struct {
+		Width               int32
+		Height              int32
+		Turn                int32
+		ShrinkEveryNTurns   int32
+		Error               error
+		ExpectedOutOfBounds []Point
+	}{
+		{Error: errors.New("royale game must shrink at least every 1 turn")},
+		{ShrinkEveryNTurns: 1, ExpectedOutOfBounds: []Point{}},
+		{Turn: 1, ShrinkEveryNTurns: 1, ExpectedOutOfBounds: []Point{}},
+		{Width: 3, Height: 3, Turn: 1, ShrinkEveryNTurns: 10, ExpectedOutOfBounds: []Point{}},
+		{Width: 3, Height: 3, Turn: 9, ShrinkEveryNTurns: 10, ExpectedOutOfBounds: []Point{}},
+		{
+			Width: 3, Height: 3, Turn: 10, ShrinkEveryNTurns: 10,
+			ExpectedOutOfBounds: []Point{{0, 0}, {0, 1}, {0, 2}, {1, 0}, {1, 2}, {2, 0}, {2, 1}, {2, 2}},
+		},
+		{
+			Width: 3, Height: 3, Turn: 11, ShrinkEveryNTurns: 10,
+			ExpectedOutOfBounds: []Point{{0, 0}, {0, 1}, {0, 2}, {1, 0}, {1, 2}, {2, 0}, {2, 1}, {2, 2}},
+		},
+		{
+			Width: 3, Height: 3, Turn: 19, ShrinkEveryNTurns: 10,
+			ExpectedOutOfBounds: []Point{{0, 0}, {0, 1}, {0, 2}, {1, 0}, {1, 2}, {2, 0}, {2, 1}, {2, 2}},
+		},
+		{
+			Width: 3, Height: 3, Turn: 20, ShrinkEveryNTurns: 10,
+			ExpectedOutOfBounds: []Point{{0, 0}, {0, 1}, {0, 2}, {1, 0}, {1, 1}, {1, 2}, {2, 0}, {2, 1}, {2, 2}},
+		},
+	}
+
+	for _, test := range tests {
+		b := &BoardState{Width: test.Width, Height: test.Height}
+		r := RoyaleRuleset{
+			Turn:              test.Turn,
+			ShrinkEveryNTurns: test.ShrinkEveryNTurns,
+		}
+
+		err := r.populateOutOfBounds(b)
+		require.Equal(t, test.Error, err)
+		if err == nil {
+			// Obstacles should match
+			require.Equal(t, test.ExpectedOutOfBounds, r.OutOfBounds)
+			for _, expectedP := range test.ExpectedOutOfBounds {
+				wasFound := false
+				for _, actualP := range r.OutOfBounds {
+					if expectedP == actualP {
+						wasFound = true
+						break
+					}
+				}
+				require.True(t, wasFound)
+			}
+		}
+	}
+}
+
+func TestRoyaleEliminateOutOfBounds(t *testing.T) {
+	tests := []struct {
+		Snakes                   []Snake
+		OutOfBounds              []Point
+		ExpectedEliminatedCauses []string
+		ExpectedEliminatedByIDs  []string
+	}{
+		{},
+		{
+			Snakes:                   []Snake{{Body: []Point{{0, 0}}}},
+			OutOfBounds:              []Point{},
+			ExpectedEliminatedCauses: []string{NotEliminated},
+			ExpectedEliminatedByIDs:  []string{""},
+		},
+		{
+			Snakes:                   []Snake{{Body: []Point{{0, 0}}}},
+			OutOfBounds:              []Point{{0, 0}},
+			ExpectedEliminatedCauses: []string{EliminatedByOutOfBounds},
+			ExpectedEliminatedByIDs:  []string{""},
+		},
+		{
+			Snakes:                   []Snake{{Body: []Point{{0, 0}, {1, 0}, {2, 0}}}},
+			OutOfBounds:              []Point{{1, 0}, {2, 0}},
+			ExpectedEliminatedCauses: []string{NotEliminated},
+			ExpectedEliminatedByIDs:  []string{""},
+		},
+		{
+			Snakes: []Snake{
+				{Body: []Point{{0, 0}, {1, 0}, {2, 0}}},
+				{Body: []Point{{3, 3}, {3, 4}, {3, 5}, {3, 6}}},
+			},
+			OutOfBounds:              []Point{{1, 0}, {2, 0}, {3, 4}, {3, 5}, {3, 6}},
+			ExpectedEliminatedCauses: []string{NotEliminated, NotEliminated},
+			ExpectedEliminatedByIDs:  []string{"", ""},
+		},
+		{
+			Snakes: []Snake{
+				{Body: []Point{{0, 0}, {1, 0}, {2, 0}}},
+				{Body: []Point{{3, 3}, {3, 4}, {3, 5}, {3, 6}}},
+			},
+			OutOfBounds:              []Point{{3, 3}},
+			ExpectedEliminatedCauses: []string{NotEliminated, EliminatedByOutOfBounds},
+			ExpectedEliminatedByIDs:  []string{"", ""},
+		},
+	}
+
+	for _, test := range tests {
+		b := &BoardState{Snakes: test.Snakes}
+		r := RoyaleRuleset{OutOfBounds: test.OutOfBounds}
+		err := r.eliminateOutOfBounds(b)
+		require.NoError(t, err)
+
+		for i, snake := range b.Snakes {
+			require.Equal(t, test.ExpectedEliminatedCauses[i], snake.EliminatedCause)
+		}
+
+	}
+}