diff --git a/src/geom.c b/src/geom.c
index d14e651..c33004a 100644
--- a/src/geom.c
+++ b/src/geom.c
@@ -24,3 +24,8 @@ bool tri_within(Pt pt, Tri* tri) {
     double c = 1 - a - b;
     return 0 <= a && a <= 1 && 0 <= b && b <= 1 && 0 <= c && c <= 1;
 }
+
+Pt tri_center(Tri* tri) {
+    return (Pt){(tri->a.x + tri->b.x + tri->c.x) / 3.0,
+                (tri->a.y + tri->b.y + tri->c.y) / 3.0};
+}
diff --git a/src/include/geom.h b/src/include/geom.h
index 66b75d0..7abf65f 100644
--- a/src/include/geom.h
+++ b/src/include/geom.h
@@ -32,6 +32,9 @@ void tri_destroy(Tri* tri);
 // Check if a point is within the triangle. Uses barycentric coordinate system.
 bool tri_within(Pt pt, Tri* tri);
 
+// Get the center point of a Tri.
+Pt tri_center(Tri* tri);
+
 typedef struct {
     Color col;
     size_t ntris;
diff --git a/src/include/util.h b/src/include/util.h
index f9a7d6e..d842515 100644
--- a/src/include/util.h
+++ b/src/include/util.h
@@ -1,9 +1,9 @@
 #ifndef UTIL_H
 #define UTIL_H
 
-#define MAX(a, b) a ? a > b : b
-#define MAX3(a, b, c) MAX(a, MAX(b, c))
-#define MIN(a, b) a ? a < b : b
-#define MIN3(a, b, c) MIN(a, MIN(b, c))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define MAX3(a, b, c) (MAX((a), MAX((b), (c))))
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define MIN3(a, b, c) (MIN((a), MIN((b), (c))))
 
 #endif
diff --git a/src/render.c b/src/render.c
index 7c07bb2..ede028e 100644
--- a/src/render.c
+++ b/src/render.c
@@ -27,16 +27,19 @@ void draw_tri(Tri* tri) {
     );
 }
 
-// bad.
 void draw_tri_inside(Tri* tri, Color col) {
-    // int maxx = MAX3(tri->a.x, tri->b.x, tri->c.x);
-    // int maxy = MAX3(tri->a.y, tri->b.y, tri->c.y);
-    // int minx = MIN3(tri->a.y, tri->b.y, tri->c.y);
-    // int miny = MIN3(tri->a.y, tri->b.y, tri->c.y);
-    for (int x = 0; x <= WORLD_SZ; x++) {
-        for (int y = 0; y < WORLD_SZ; y++) {
+    int maxx = MAX3(tri->a.x, tri->b.x, tri->c.x);
+    int maxy = MAX3(tri->a.y, tri->b.y, tri->c.y);
+    int minx = MIN3(tri->a.x, tri->b.x, tri->c.x);
+    int miny = MIN3(tri->a.y, tri->b.y, tri->c.y);
+    for (int x = minx; x <= maxx; x++) {
+        for (int y = miny; y <= maxy; y++) {
             if (tri_within((Pt){x, y}, tri)) {
-                DrawCircleV(PointToVector2((Pt){x, y}), 4.f, col);
+                // DrawCircleV(PointToVector2((Pt){x, y}), 4.f, col);
+                DrawLineV(
+                    PointToVector2((Pt){x, y}), PointToVector2(tri_center(tri)),
+                    col
+                );
             }
         }
     }