diff --git a/src/limit.rs b/src/limit.rs
index a8910ce..5812c94 100644
--- a/src/limit.rs
+++ b/src/limit.rs
@@ -4,14 +4,52 @@ use serde::{Deserialize, Serialize};
 /// Limit wrapper
 pub struct Limit {
     /// lower limit
-    pub min: f64,
+    min: f64,
     /// upper limit
-    pub max: f64,
+    max: f64,
 }
 
 impl Limit {
+    /// Create new limit
+    pub fn new(min: f64, max: f64) -> Self {
+        if min > max {
+            panic!("min must be less than max");
+        }
+        Self { min, max }
+    }
+
+    /// lower limit
+    pub fn min(&self) -> f64 {
+        self.min
+    }
+
+    /// upper limit
+    pub fn max(&self) -> f64 {
+        self.max
+    }
+
     /// Clamp value to limits
     pub fn clamp(&self, value: f64) -> f64 {
         value.clamp(self.min, self.max)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::Limit;
+
+    #[test]
+    #[should_panic]
+    fn bad_limit() {
+        Limit::new(1.0, -1.0);
+    }
+
+    #[test]
+    fn check_limit() {
+        let limit = Limit::new(-1.0, 1.0);
+
+        assert_eq!(limit.clamp(-2.0), -1.0);
+        assert_eq!(limit.clamp(0.0), 0.0);
+        assert_eq!(limit.clamp(2.0), 1.0);
+    }
+}