diff --git a/internal/geom/fit.go b/internal/geom/fit.go
new file mode 100644
index 0000000..cfa672a
--- /dev/null
+++ b/internal/geom/fit.go
@@ -0,0 +1,25 @@
+package geom
+
+import "math"
+
+type AABB struct{ Min, Max Vec }
+
+func Bounds(pts []Vec) AABB {
+	minX, minY := math.Inf(1), math.Inf(1)
+	maxX, maxY := math.Inf(-1), math.Inf(-1)
+	for _, p := range pts {
+		if p.X < minX {
+			minX = p.X
+		}
+		if p.Y < minY {
+			minY = p.Y
+		}
+		if p.X > maxX {
+			maxX = p.X
+		}
+		if p.Y > maxY {
+			maxY = p.Y
+		}
+	}
+	return AABB{Min: V(minX, minY), Max: V(maxX, maxY)}
+}
diff --git a/internal/geom/intersect.go b/internal/geom/intersect.go
new file mode 100644
index 0000000..fc868de
--- /dev/null
+++ b/internal/geom/intersect.go
@@ -0,0 +1,11 @@
+package geom
+
+func SegLineIntersect(A, B, O, D Vec) (bool, float64) {
+	r := Sub(B, A)
+	den := Cross(r, D)
+	if NearlyZero(den) {
+		return false, 0
+	}
+	t := Cross(Sub(O, A), D) / den
+	return t > EPS && t < 1-EPS, t
+}