diff --git a/src/main/kotlin/rps/Game.kt b/src/main/kotlin/rps/Game.kt
index 2606fe5..a9e23f1 100644
--- a/src/main/kotlin/rps/Game.kt
+++ b/src/main/kotlin/rps/Game.kt
@@ -4,11 +4,17 @@ fun main() {
   println("Hello, world")
 }
 
-/** A possible move in a game of rock-paper-scissors. */
-enum class Move {
-  ROCK,
-  PAPER,
-  SCISSORS
+/**
+ * A possible move in a game of rock-paper-scissors.
+ *
+ * [strongAgainst] is a function for lazy evaluation because otherwise we can’t access SCISSORS before it’s been defined.
+ * If the game needs to be expanded (e.g. the somewhat common “rock, paper, scissors, salamander, spock”),
+ * this argument could be a List<Move> instead.
+ */
+enum class Move(val strongAgainst: () -> Move) {
+  ROCK({ SCISSORS }),
+  PAPER({ ROCK }),
+  SCISSORS({ PAPER })
 }
 
 // purposely not calling this Result to avoid confusion with kotlin.Result and similar
@@ -19,4 +25,8 @@ enum class Outcome {
 }
 
 /** Determine the [Outcome] of [first] vs [second] from the perspective of [first]. */
-fun determineOutcome(first: Move, second: Move): Outcome = TODO()
\ No newline at end of file
+fun determineOutcome(first: Move, second: Move): Outcome = when {
+  first.strongAgainst() == second -> Outcome.WIN
+  first == second -> Outcome.DRAW
+  else -> Outcome.LOSS
+}
\ No newline at end of file