diff --git a/src/engine.py b/src/engine.py
index aa1bfa5..0816805 100644
--- a/src/engine.py
+++ b/src/engine.py
@@ -1,5 +1,6 @@
 from decimal import Decimal
 import logging
+import math
 
 from models import (
     EngineFixture,
@@ -67,27 +68,18 @@ class Engine:
                 continue
             still_running = True
 
-            # Move keyframes forward
+            # Move track forward
             t.step(step_size)
             if t.current is None:
-                raise BaseException(f"Track has no current keyframes.")
+                raise BaseException(f"Track has no current keyframe.")
 
-            # Interpolate over keyframes of track
-            for k in t.current:
-                
-                next_value: KeyframeValue = None
-                if t.next:
-                    try:
-                        next_value = t.next.get(k.parameter).value
-                    except:
-                        pass    # next_value already None by default
-                
-                interpolated_value = self.interpolate_value(k.value, next_value, k.interpolation)
+            # Interpolate and update value
+            interpolated_value = self.get_current_value(t)
 
-                # Update values of relevant fixtures
-                for f in self.fixtures.values():
-                    if f.fixture.id in t.track.fixture_ids:
-                        f.set(k.parameter, interpolated_value)
+            # Update values of relevant fixtures
+            for f in self.fixtures.values():
+                if f.fixture.id in t.track.fixture_ids:
+                    f.set(t.track.parameter, interpolated_value)
 
         # Update running state
         self.is_running = still_running
@@ -100,11 +92,97 @@ class Engine:
             api = self.apis[f.fixture.api]
             # TODO: Pass update to API
 
+    def get_current_value(self, track: EngineTrack) -> KeyframeValue:
+        """Interpolate between current keyframes of track and return the interpolated value."""
+        current = track.current
+        if current is None:
+            raise BaseException(
+                f"Track has no current keyframe. Cannot interpolate values."
+            )
+
+        next = track.next
+        if next is None:
+            return current.frame.value
+
+        t = current.delta.copy_abs() / (
+            current.delta.copy_abs() + next.delta.copy_abs()
+        )
+
+        return self.interpolate_value(
+            current.frame.value, next.frame.value, t, current.frame.interpolation
+        )
+
     def interpolate_value(
-        self, current: KeyframeValue, next: KeyframeValue, interpolation: Interpolation
-    ) -> KeyframeValue:
-        """Interpolate between two keyframe values and return the interpolated value."""
-        cur_frame: Keyframe = current.get(parameter)
-        if  
-        # TODO
-        return current.get(parameter).value
+        self,
+        start: KeyframeValue,
+        end: KeyframeValue,
+        t: Decimal,
+        interpolation: Interpolation,
+    ):
+        """CHATGPT. Interpolate between two numeric values with given interpolation type.
+        t is normalized between 0.0 (start) and 1.0 (end)."""
+
+        if not isinstance(start, (int, float)) or not isinstance(end, (int, float)):
+            logging.warning(
+                f"Interpolation [{interpolation}] only supported for int/float. "
+                f"Got {type(start)} → {start}, {type(end)} → {end}. Falling back to STEP."
+            )
+            return end  # default STEP behavior
+
+        # Clamp t for safety
+        t = max(Decimal.from_float(0), min(Decimal.from_float(1), t))
+
+        match interpolation:
+            case Interpolation.STEP:
+                return end
+            case Interpolation.LINEAR:
+                f = t
+            case Interpolation.EASE_IN:
+                f = t * t
+            case Interpolation.EASE_OUT:
+                f = 1 - (1 - t) * (1 - t)
+            case Interpolation.EASE_IN_OUT:
+                f = 2 * t * t if t < 0.5 else 1 - pow(-2 * t + 2, 2) / 2
+            case Interpolation.EXPONENTIAL:
+                f = pow(2, 10 * (t - 1)) if t > 0 else 0
+            case Interpolation.LOGARITHMIC:
+                f = math.log10(9 * t + 1)  # maps 0→0, 1→1 smoothly
+            case Interpolation.SINE:
+                f = 0.5 - 0.5 * math.cos(Decimal.from_float(math.pi) * t)
+            case Interpolation.SMOOTHSTEP:
+                f = t * t * (3 - 2 * t)
+            case Interpolation.BOUNCE:
+                f = self.bounce_out(float(t))
+            case Interpolation.ELASTIC:
+                f = self.elastic_out(t)
+            case _:
+                logging.warning(
+                    f"Unhandled interpolation type [{interpolation}]. Using STEP."
+                )
+                return end
+
+        raise BaseException("Unreachable code reached.")
+
+    def bounce_out(self, t: float) -> float:
+        """CHATGPT. Bounce easing function (out)."""
+        n1, d1 = 7.5625, 2.75
+        if t < 1 / d1:
+            return n1 * t * t
+        elif t < 2 / d1:
+            t -= 1.5 / d1
+            return n1 * t * t + 0.75
+        elif t < 2.5 / d1:
+            t -= 2.25 / d1
+            return n1 * t * t + 0.9375
+        else:
+            t -= 2.625 / d1
+            return n1 * t * t + 0.984375
+
+    def elastic_out(self, t: Decimal) -> float:
+        """CHATGPT. Elastic easing function (out)."""
+        c4 = (2 * math.pi) / 3
+        if t == 0:
+            return 0
+        if t == 1:
+            return 1
+        return pow(2, -10 * t) * math.sin((float(t) * 10 - 0.75) * c4) + 1
diff --git a/src/models.py b/src/models.py
index 98b955c..cc7693e 100644
--- a/src/models.py
+++ b/src/models.py
@@ -151,6 +151,12 @@ class Interpolation(Enum):
     EASE_IN_OUT = "ease-in-out"
     EASE_IN = "ease-in"
     EASE_OUT = "ease-out"
+    EXPONENTIAL = "exponential"
+    LOGARITHMIC = "logarithmic"
+    SINE = "sine"
+    SMOOTHSTEP = "smoothstep"
+    BOUNCE = "bounce"
+    ELASTIC = "elastic"
 
 
 @dataclass_json