diff --git a/rust/clock/src/lib.rs b/rust/clock/src/lib.rs
index c625f73..d3f0573 100644
--- a/rust/clock/src/lib.rs
+++ b/rust/clock/src/lib.rs
@@ -1,11 +1,120 @@
-pub struct Clock;
+use std::fmt::{Display, Formatter, self};
+
+const HOURS_PER_DAY: i32 = 24;
+const MINUTES_PER_HOUR: i32 = 60;
+type MinutesSinceMidnight = RingI32<{ HOURS_PER_DAY * MINUTES_PER_HOUR }>;
+
+const HOUR_SINCE_MIDNIGHT: MinutesSinceMidnight = MinutesSinceMidnight::new(MINUTES_PER_HOUR);
+
+#[derive(Debug, PartialEq)]
+pub struct Clock {
+    since_midnight: MinutesSinceMidnight,
+}
 
 impl Clock {
     pub fn new(hours: i32, minutes: i32) -> Self {
-        todo!("Construct a new Clock from {hours} hours and {minutes} minutes");
+        let since_midnight = MinutesSinceMidnight::new(minutes);
+        let since_midnight = HOUR_SINCE_MIDNIGHT * hours + since_midnight;
+        Self {
+            since_midnight,
+        }
     }
 
     pub fn add_minutes(&self, minutes: i32) -> Self {
-        todo!("Add {minutes} minutes to existing Clock time");
+        let since_midnight = self.since_midnight + minutes;
+        Self {
+            since_midnight,
+        }
+    }
+}
+
+impl Display for Clock {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        let hours = self.since_midnight / HOUR_SINCE_MIDNIGHT;
+        let minutes = self.since_midnight % HOUR_SINCE_MIDNIGHT;
+        write!(f, "{hours:02}:{minutes:02}")
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+struct RingI32<const N: i32>(i32);
+
+impl<const N: i32> RingI32<N> {
+    const fn new(v: i32) -> Self {
+        Self(v.rem_euclid(N))
+    }
+
+    const fn val(&self) -> i32 {
+        self.0
+    }
+}
+
+impl<const N: i32> Display for RingI32<N> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<const N: i32> std::ops::Add<i32> for RingI32<N> {
+    type Output = Self;
+    fn add(self, rhs: i32) -> Self {
+        let lhs = self.val();
+        let rhs = rhs.rem_euclid(N);
+        Self((lhs + rhs).rem_euclid(N))
+    }
+}
+
+impl<const N: i32> std::ops::Mul<i32> for RingI32<N> {
+    type Output = Self;
+    fn mul(self, rhs: i32) -> Self {
+        let lhs = self.val();
+        let rhs = rhs.rem_euclid(N);
+        Self((lhs * rhs).rem_euclid(N))
+    }
+}
+
+impl<const N: i32> std::ops::Div<i32> for RingI32<N> {
+    type Output = Self;
+    fn div(self, rhs: i32) -> Self {
+        let lhs = self.val();
+        let rhs = rhs.rem_euclid(N);
+        Self((lhs / rhs).rem_euclid(N))
+    }
+}
+
+impl<const N: i32> std::ops::Rem<i32> for RingI32<N> {
+    type Output = Self;
+    fn rem(self, rhs: i32) -> Self {
+        let lhs = self.val();
+        let rhs = rhs.rem_euclid(N);
+        Self((lhs % rhs).rem_euclid(N))
+    }
+}
+
+impl<const N: i32> std::ops::Add for RingI32<N> {
+    type Output = Self;
+    fn add(self, rhs: Self) -> Self {
+        self + rhs.val()
+    }
+}
+
+impl<const N: i32> std::ops::Mul for RingI32<N> {
+    type Output = Self;
+    fn mul(self, rhs: Self) -> Self {
+        self * rhs.val()
+    }
+}
+
+impl<const N: i32> std::ops::Div for RingI32<N> {
+    type Output = Self;
+    fn div(self, rhs: Self) -> Self {
+        self / rhs.val()
+    }
+}
+
+impl<const N: i32> std::ops::Rem for RingI32<N> {
+    type Output = Self;
+    fn rem(self, rhs: Self) -> Self {
+        self % rhs.val()
     }
 }
diff --git a/rust/clock/tests/clock.rs b/rust/clock/tests/clock.rs
index 416a6f9..9e70400 100644
--- a/rust/clock/tests/clock.rs
+++ b/rust/clock/tests/clock.rs
@@ -10,127 +10,106 @@ fn on_the_hour() {
 }
 
 #[test]
-#[ignore]
 fn past_the_hour() {
     assert_eq!(Clock::new(11, 9).to_string(), "11:09");
 }
 
 #[test]
-#[ignore]
 fn midnight_is_zero_hours() {
     assert_eq!(Clock::new(24, 0).to_string(), "00:00");
 }
 
 #[test]
-#[ignore]
 fn hour_rolls_over() {
     assert_eq!(Clock::new(25, 0).to_string(), "01:00");
 }
 
 #[test]
-#[ignore]
 fn hour_rolls_over_continuously() {
     assert_eq!(Clock::new(100, 0).to_string(), "04:00");
 }
 
 #[test]
-#[ignore]
 fn sixty_minutes_is_next_hour() {
     assert_eq!(Clock::new(1, 60).to_string(), "02:00");
 }
 
 #[test]
-#[ignore]
 fn minutes_roll_over() {
     assert_eq!(Clock::new(0, 160).to_string(), "02:40");
 }
 
 #[test]
-#[ignore]
 fn minutes_roll_over_continuously() {
     assert_eq!(Clock::new(0, 1723).to_string(), "04:43");
 }
 
 #[test]
-#[ignore]
 fn hours_and_minutes_roll_over() {
     assert_eq!(Clock::new(25, 160).to_string(), "03:40");
 }
 
 #[test]
-#[ignore]
 fn hours_and_minutes_roll_over_continuously() {
     assert_eq!(Clock::new(201, 3001).to_string(), "11:01");
 }
 
 #[test]
-#[ignore]
 fn hours_and_minutes_roll_over_to_exactly_midnight() {
     assert_eq!(Clock::new(72, 8640).to_string(), "00:00");
 }
 
 #[test]
-#[ignore]
 fn negative_hour() {
     assert_eq!(Clock::new(-1, 15).to_string(), "23:15");
 }
 
 #[test]
-#[ignore]
 fn negative_hour_roll_over() {
     assert_eq!(Clock::new(-25, 00).to_string(), "23:00");
 }
 
 #[test]
-#[ignore]
 fn negative_hour_roll_over_continuously() {
     assert_eq!(Clock::new(-91, 00).to_string(), "05:00");
 }
 
 #[test]
-#[ignore]
 fn negative_minutes() {
     assert_eq!(Clock::new(1, -40).to_string(), "00:20");
 }
 
 #[test]
-#[ignore]
 fn negative_minutes_roll_over() {
     assert_eq!(Clock::new(1, -160).to_string(), "22:20");
 }
 
 #[test]
-#[ignore]
 fn negative_minutes_roll_over_continuously() {
     assert_eq!(Clock::new(1, -4820).to_string(), "16:40");
 }
 
 #[test]
-#[ignore]
 fn negative_sixty_minutes_is_prev_hour() {
     assert_eq!(Clock::new(2, -60).to_string(), "01:00");
 }
 
 #[test]
-#[ignore]
 fn negative_one_twenty_minutes_is_two_prev_hours() {
     assert_eq!(Clock::new(1, -120).to_string(), "23:00");
 }
 
 #[test]
-#[ignore]
 fn negative_hour_and_minutes_both_roll_over() {
     assert_eq!(Clock::new(-25, -160).to_string(), "20:20");
 }
 
 #[test]
-#[ignore]
 fn negative_hour_and_minutes_both_roll_over_continuously() {
     assert_eq!(Clock::new(-121, -5810).to_string(), "22:10");
 }
 
 #[test]
-#[ignore]
 fn zero_hour_and_negative_minutes() {
     assert_eq!(Clock::new(0, -22).to_string(), "23:38");
 }
@@ -140,112 +119,96 @@ fn zero_hour_and_negative_minutes() {
 //
 
 #[test]
-#[ignore]
 fn add_minutes() {
     let clock = Clock::new(10, 0).add_minutes(3);
     assert_eq!(clock.to_string(), "10:03");
 }
 
 #[test]
-#[ignore]
 fn add_no_minutes() {
     let clock = Clock::new(6, 41).add_minutes(0);
     assert_eq!(clock.to_string(), "06:41");
 }
 
 #[test]
-#[ignore]
 fn add_to_next_hour() {
     let clock = Clock::new(0, 45).add_minutes(40);
     assert_eq!(clock.to_string(), "01:25");
 }
 
 #[test]
-#[ignore]
 fn add_more_than_one_hour() {
     let clock = Clock::new(10, 0).add_minutes(61);
     assert_eq!(clock.to_string(), "11:01");
 }
 
 #[test]
-#[ignore]
 fn add_more_than_two_hours_with_carry() {
     let clock = Clock::new(0, 45).add_minutes(160);
     assert_eq!(clock.to_string(), "03:25");
 }
 
 #[test]
-#[ignore]
 fn add_across_midnight() {
     let clock = Clock::new(23, 59).add_minutes(2);
     assert_eq!(clock.to_string(), "00:01");
 }
 
 #[test]
-#[ignore]
 fn add_more_than_one_day() {
     let clock = Clock::new(5, 32).add_minutes(1500);
     assert_eq!(clock.to_string(), "06:32");
 }
 
 #[test]
-#[ignore]
 fn add_more_than_two_days() {
     let clock = Clock::new(1, 1).add_minutes(3500);
     assert_eq!(clock.to_string(), "11:21");
 }
 
 #[test]
-#[ignore]
 fn subtract_minutes() {
     let clock = Clock::new(10, 3).add_minutes(-3);
     assert_eq!(clock.to_string(), "10:00");
 }
 
 #[test]
-#[ignore]
 fn subtract_to_previous_hour() {
     let clock = Clock::new(10, 3).add_minutes(-30);
     assert_eq!(clock.to_string(), "09:33");
 }
 
 #[test]
-#[ignore]
 fn subtract_more_than_an_hour() {
     let clock = Clock::new(10, 3).add_minutes(-70);
     assert_eq!(clock.to_string(), "08:53");
 }
 
 #[test]
-#[ignore]
 fn subtract_across_midnight() {
     let clock = Clock::new(0, 3).add_minutes(-4);
     assert_eq!(clock.to_string(), "23:59");
 }
 
 #[test]
-#[ignore]
 fn subtract_more_than_two_hours() {
     let clock = Clock::new(0, 0).add_minutes(-160);
     assert_eq!(clock.to_string(), "21:20");
 }
 
 #[test]
-#[ignore]
 fn subtract_more_than_two_hours_with_borrow() {
     let clock = Clock::new(6, 15).add_minutes(-160);
     assert_eq!(clock.to_string(), "03:35");
 }
 
 #[test]
-#[ignore]
 fn subtract_more_than_one_day() {
     let clock = Clock::new(5, 32).add_minutes(-1500);
     assert_eq!(clock.to_string(), "04:32");
 }
 
 #[test]
-#[ignore]
 fn subtract_more_than_two_days() {
     let clock = Clock::new(2, 20).add_minutes(-3000);
     assert_eq!(clock.to_string(), "00:20");
@@ -256,97 +219,81 @@ fn subtract_more_than_two_days() {
 //
 
 #[test]
-#[ignore]
 fn compare_clocks_for_equality() {
     assert_eq!(Clock::new(15, 37), Clock::new(15, 37));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_a_minute_apart() {
     assert_ne!(Clock::new(15, 36), Clock::new(15, 37));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_an_hour_apart() {
     assert_ne!(Clock::new(14, 37), Clock::new(15, 37));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_hour_overflow() {
     assert_eq!(Clock::new(10, 37), Clock::new(34, 37));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_hour_overflow_by_several_days() {
     assert_eq!(Clock::new(99, 11), Clock::new(3, 11));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_hour() {
     assert_eq!(Clock::new(-2, 40), Clock::new(22, 40));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_hour_that_wraps() {
     assert_eq!(Clock::new(-31, 3), Clock::new(17, 3));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_hour_that_wraps_multiple_times() {
     assert_eq!(Clock::new(-83, 49), Clock::new(13, 49));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_minutes_overflow() {
     assert_eq!(Clock::new(0, 1441), Clock::new(0, 1));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_minutes_overflow_by_several_days() {
     assert_eq!(Clock::new(2, 4322), Clock::new(2, 2));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_minute() {
     assert_eq!(Clock::new(3, -20), Clock::new(2, 40));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_minute_that_wraps() {
     assert_eq!(Clock::new(5, -1490), Clock::new(4, 10));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_minute_that_wraps_multiple() {
     assert_eq!(Clock::new(6, -4305), Clock::new(6, 15));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_hours_and_minutes() {
     assert_eq!(Clock::new(-12, -268), Clock::new(7, 32));
 }
 
 #[test]
-#[ignore]
 fn compare_clocks_with_negative_hours_and_minutes_that_wrap() {
     assert_eq!(Clock::new(-54, -11_513), Clock::new(18, 7));
 }
 
 #[test]
-#[ignore]
 fn compare_full_clock_and_zeroed_clock() {
     assert_eq!(Clock::new(24, 0), Clock::new(0, 0));
 }