diff --git a/26_T1/afl_player_tracking_and_crowd_monitoring/Crowd_Monitoring/2026_T1/heatmap/main.py b/26_T1/afl_player_tracking_and_crowd_monitoring/Crowd_Monitoring/2026_T1/heatmap/main.py
index d933869f..3fa64d50 100644
--- a/26_T1/afl_player_tracking_and_crowd_monitoring/Crowd_Monitoring/2026_T1/heatmap/main.py
+++ b/26_T1/afl_player_tracking_and_crowd_monitoring/Crowd_Monitoring/2026_T1/heatmap/main.py
@@ -8,60 +8,124 @@
 import numpy as np
 
 
+def validate_input(input_data: Dict) -> None:
+    """Validate incoming heatmap input data."""
+    if not isinstance(input_data, dict):
+        raise ValueError("Input data must be a dictionary.")
+
+    if "video_id" not in input_data or not input_data["video_id"]:
+        raise ValueError("Missing or empty 'video_id'.")
+
+    if "zones" not in input_data:
+        raise ValueError("Missing 'zones' field.")
+
+    if not isinstance(input_data["zones"], list):
+        raise ValueError("'zones' must be a list.")
+
+    if len(input_data["zones"]) == 0:
+        raise ValueError("'zones' list cannot be empty.")
+
+    required_zone_fields = {"zone_id", "person_count", "density"}
+
+    for index, zone in enumerate(input_data["zones"]):
+        if not isinstance(zone, dict):
+            raise ValueError(f"Zone at index {index} must be a dictionary.")
+
+        missing_fields = required_zone_fields - zone.keys()
+        if missing_fields:
+            raise ValueError(
+                f"Zone at index {index} is missing fields: {', '.join(sorted(missing_fields))}"
+            )
+
+
 def generate_heatmap(input_data: Dict) -> Dict:
-    """Generate a basic heatmap image from zone density data."""
+    """Generate a validated and schema-compliant heatmap image from zone density data."""
+    validate_input(input_data)
 
-    video_id = input_data["video_id"]
+    video_id = str(input_data["video_id"])
     zones: List[Dict] = input_data["zones"]
 
-    if not zones:
-        raise ValueError("Zones list is empty.")
-
     output_dir = "output"
     os.makedirs(output_dir, exist_ok=True)
 
-    densities = [zone["density"] for zone in zones]
-    zone_ids = [zone["zone_id"] for zone in zones]
-
     num_zones = len(zones)
     cols = int(np.ceil(np.sqrt(num_zones)))
     rows = int(np.ceil(num_zones / cols))
 
-    heatmap_array = np.zeros((rows, cols))
+    heatmap_array = np.full((rows, cols), np.nan)
     labels = [["" for _ in range(cols)] for _ in range(rows)]
 
     for index, zone in enumerate(zones):
         row = index // cols
         col = index % cols
-        heatmap_array[row, col] = zone["density"]
-        labels[row][col] = f"{zone['zone_id']}\nCount: {zone['person_count']}\nDensity: {zone['density']:.2f}"
+
+        zone_id = str(zone["zone_id"])
+
+        try:
+            density = float(zone["density"])
+        except (TypeError, ValueError):
+            raise ValueError(f"Density for zone '{zone_id}' must be numeric.")
+
+        density = max(0.0, min(1.0, density))
+
+        try:
+            person_count = int(zone["person_count"])
+        except (TypeError, ValueError):
+            raise ValueError(f"Person count for zone '{zone_id}' must be an integer.")
+
+        heatmap_array[row, col] = density
+        labels[row][col] = (
+            f"{zone_id}\n"
+            f"Count: {person_count}\n"
+            f"Density: {density:.2f}"
+        )
 
     fig, ax = plt.subplots(figsize=(8, 6))
-    im = ax.imshow(heatmap_array, cmap="hot", interpolation="nearest")
+
+    cmap = plt.cm.YlOrRd.copy()
+    cmap.set_bad(color="lightgrey")
+
+    im = ax.imshow(
+        heatmap_array,
+        cmap=cmap,
+        interpolation="nearest",
+        vmin=0,
+        vmax=1,
+    )
 
     for row in range(rows):
         for col in range(cols):
             if labels[row][col]:
+                cell_value = heatmap_array[row, col]
+
+                if np.isnan(cell_value):
+                    text_color = "black"
+                else:
+                    text_color = "black" if cell_value <= 0.35 or cell_value >= 0.65 else "white"
+
                 ax.text(
                     col,
                     row,
                     labels[row][col],
                     ha="center",
                     va="center",
-                    color="white",
-                    fontsize=9,
+                    color=text_color,
+                    fontsize=10,
+                    fontweight="bold",
                 )
 
-    ax.set_title(f"Heatmap for {video_id}")
-    ax.set_xticks([])
-    ax.set_yticks([])
+    ax.set_title(f"Heatmap for {video_id}", fontsize=16, fontweight="bold")
+    ax.set_xticks(np.arange(-0.5, cols, 1), minor=True)
+    ax.set_yticks(np.arange(-0.5, rows, 1), minor=True)
+    ax.grid(which="minor", color="black", linestyle="-", linewidth=1.5)
+    ax.tick_params(which="both", bottom=False, left=False, labelbottom=False, labelleft=False)
 
     cbar = plt.colorbar(im, ax=ax)
-    cbar.set_label("Density")
+    cbar.set_label("Density", fontsize=12)
 
     image_path = os.path.join(output_dir, f"heatmap_{video_id}.png")
     plt.tight_layout()
-    plt.savefig(image_path, dpi=200)
+    plt.savefig(image_path, dpi=200, bbox_inches="tight")
     plt.close()
 
     return {
@@ -74,12 +138,12 @@ def generate_heatmap(input_data: Dict) -> Dict:
 
 if __name__ == "__main__":
     sample_input = {
-        "video_id": "match_01",
+        "video_id": "match_02",
         "zones": [
-            {"zone_id": "A1", "person_count": 8, "density": 0.72},
-            {"zone_id": "A2", "person_count": 5, "density": 0.45},
-            {"zone_id": "A3", "person_count": 10, "density": 0.88},
-            {"zone_id": "A4", "person_count": 3, "density": 0.20},
+            {"zone_id": "A1", "person_count": 2, "density": 0.10},
+            {"zone_id": "A2", "person_count": 6, "density": 0.55},
+            {"zone_id": "A3", "person_count": 12, "density": 0.95},
+            {"zone_id": "A4", "person_count": 4, "density": 0.30},
         ],
     }