Created a simple PairCondition class for pairing inputs together

Source/PairCondition.cs

@@ -0,0 +1,61 @@
+namespace Apos.Input
+{
+    /// <summary>
+    /// A condition that tracks multiple inputs along a single dimension.
+    /// </summary>
+    public class PairCondition : ICondition {
+        readonly ICondition _negativeCondition;
+
+        readonly ICondition _positiveCondition;
+
+        /// <summary>
+        /// Creates a paired condition from the two inputs.
+        /// </summary>
+        /// <param name="negative">The negative-associated input.</param>
+        /// <param name="positive">The positive-associated input.</param>
+        public PairCondition(ICondition negative, ICondition positive) {
+            _negativeCondition = negative;
+            _positiveCondition = positive;
+        }
+
+        /// <returns>Returns true when a condition was false and is now true.</returns>
+        public bool Pressed(bool canConsume = true) {
+            return _negativeCondition.Pressed(canConsume) || _positiveCondition.Pressed(canConsume);
+        }
+
+        /// <returns>Returns true when a condition is now true.</returns>
+        public bool Held(bool canConsume = true) {
+            return _negativeCondition.Held(canConsume) || _positiveCondition.Held(canConsume);
+        }
+
+        /// <returns>Returns true when the button was pressed and is now pressed.</returns>
+        public bool HeldOnly(bool canConsume = true) {
+            return _negativeCondition.HeldOnly(canConsume) || _positiveCondition.HeldOnly(canConsume);
+        }
+
+        /// <returns>Returns true when a condition was true and is now false.</returns>
+        public bool Released(bool canConsume = true) {
+            return _negativeCondition.Released(canConsume) || _positiveCondition.Released(canConsume);
+        }
+
+        /// <summary>Does nothing since this condition isn't tracked.</summary>
+        public void Consume() { }
+
+        /// <summary>
+        /// Gets the value of this condition.
+        /// </summary>
+        /// <returns>-1 if the negative input is held; 1 if the positive input is held; 0 otherwise.</returns>
+        public float GetValue () {
+            // TODO: How do we want to handle when both inputs are active?
+            if (_negativeCondition.Held()) {
+                return -1;
+            }
+            else if (_positiveCondition.Held()) {
+                return 1;
+            }
+            else {
+                return 0;
+            }
+        }
+    }
+}