diff --git a/exercises/practice/space-age/.meta/src/example.art b/exercises/practice/space-age/.meta/src/example.art
index aa4c32b..b2b1e86 100644
--- a/exercises/practice/space-age/.meta/src/example.art
+++ b/exercises/practice/space-age/.meta/src/example.art
@@ -1,21 +1,23 @@
-earthOrbitLength: 31557600.0
+specify 'earthYear 31557600`s
+specify 'mercuryYear 0.2408467`earthYear
+specify 'venusYear 0.61519726`earthYear
+specify 'marsYear 1.8808158`earthYear
+specify 'jupiterYear 11.862615`earthYear
+specify 'saturnYear 29.447498`earthYear
+specify 'uranusYear 84.016846`earthYear
+specify 'neptuneYear 164.79132`earthYear
 
-orbitRatios: #[
-    earth:      1.0
-    mercury:    0.2408467
-    venus:      0.61519726
-    mars:       1.8808158
-    jupiter:    11.862615
-    saturn:     29.447498
-    uranus:     84.016846
-    neptune:    164.79132
+ageOn: function [planet :literal seconds :quantity][
+    earthYears: in`earthYear seconds
+    case planet [
+        'earth -> earthYears
+        'mercury -> convert earthYears `mercuryYear
+        'venus -> convert earthYears `venusYear
+        'mars -> convert earthYears `marsYear
+        'jupiter -> convert earthYears `jupiterYear
+        'saturn -> convert earthYears `saturnYear
+        'uranus -> convert earthYears `uranusYear
+        'neptune -> convert earthYears `neptuneYear
+        any -> null
+    ]
 ]
-
-ageOn: function [planet seconds][
-    planet: lower planet
-    earthAge: seconds / earthOrbitLength
-    switch key? orbitRatios planet
-        -> earthAge / orbitRatios\[planet]
-        -> null
-]
-
diff --git a/exercises/practice/space-age/src/space-age.art b/exercises/practice/space-age/src/space-age.art
index 5987e14..cecd7ba 100644
--- a/exercises/practice/space-age/src/space-age.art
+++ b/exercises/practice/space-age/src/space-age.art
@@ -1,4 +1,7 @@
-ageOn: function [planet seconds][
+; Define your custom units here to represent each planet's year
+; Be careful. We're defining a year on Earth as 31557600 seconds,
+; but the built-in `yr unit uses 31556952 seconds.
+
+ageOn: function [planet :literal seconds :quantity][
     panic "Please implement the ageOn function"
 ]
-
diff --git a/exercises/practice/space-age/tests/test-space-age.art b/exercises/practice/space-age/tests/test-space-age.art
index dc8306d..152cd3d 100644
--- a/exercises/practice/space-age/tests/test-space-age.art
+++ b/exercises/practice/space-age/tests/test-space-age.art
@@ -1,56 +1,64 @@
 import {unitt}!
 import {src/space-age}!
 
-approximately?: function [value target][ 
-    lower: value - 0.01 
-    upper: value + 0.01  
- 
-    between? target lower upper 
-] 
+approximatelyEqual?: function [value :floating target :floating][
+    lower: value - 0.01
+    upper: value + 0.01
+
+    between? target lower upper
+]
 
 suite "Space Age" [
     test "age on Earth" [
-        result: ageOn "Earth" 1000000000
-        assert -> approximately? result 31.69
+        result: to :floating ageOn 'earth 1000000000`s
+        expected: to :floating 31.69`earthYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Mercury" [
-        result: ageOn "Mercury" 2134835688
-        assert -> approximately? result 280.88
+        result: to :floating ageOn 'mercury 2134835688`s
+        expected: to :floating 280.88`mercuryYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Venus" [
-        result: ageOn "Venus" 189839836
-        assert -> approximately? result 9.78
+        result: to :floating ageOn 'venus 189839836`s
+        expected: to :floating 9.78`venusYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Mars" [
-        result: ageOn "Mars" 2129871239
-        assert -> approximately? result 35.88
+        result: to :floating ageOn 'mars 2129871239`s
+        expected: to :floating 35.88`marsYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Jupiter" [
-        result: ageOn "Jupiter" 901876382
-        assert -> approximately? result 2.41
+        result: to :floating ageOn 'jupiter 901876382`s
+        expected: to :floating 2.41`jupiterYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Saturn" [
-        result: ageOn "Saturn" 2000000000
-        assert -> approximately? result 2.15
+        result: to :floating ageOn 'saturn 2000000000`s
+        expected: to :floating 2.15`saturnYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Uranus" [
-        result: ageOn "Uranus" 1210123456
-        assert -> approximately? result 0.46
+        result: to :floating ageOn 'uranus 1210123456`s
+        expected: to :floating 0.46`uranusYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "age on Neptune" [
-        result: ageOn "Neptune" 1821023456
-        assert -> approximately? result 0.35
+        result: to :floating ageOn 'neptune 1821023456`s
+        expected: to :floating 0.35`neptuneYear
+        assert -> approximatelyEqual? result expected
     ]
     
     test.skip "invalid planet returns null" [
-        result: ageOn "Sun" 680804807
+        result: ageOn 'sun 680804807`s
         assert -> null? result
     ]
 ]