diff --git a/Nerd_STF/Mathematics/Geometry/Triangle.cs b/Nerd_STF/Mathematics/Geometry/Triangle.cs
index 3cde921..16714d8 100644
--- a/Nerd_STF/Mathematics/Geometry/Triangle.cs
+++ b/Nerd_STF/Mathematics/Geometry/Triangle.cs
@@ -1,12 +1,138 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace Nerd_STF.Mathematics.Geometry;
 
-namespace Nerd_STF.Mathematics.Geometry
+public class Triangle : IClosestTo<Float3>, IContains<Float3>,
+    IFromTuple<Triangle, (Float3 a, Float3 b, Float3 c)>, IPolygon<Triangle>,
+    ISubdivide<Triangle>, IWithinRange<Triangle>
 {
-    public class Triangle
+    public float Area
     {
+        get // Heron's Formula
+        {
+            float a = AB.Length, b = AC.Length, c = BC.Length,
+                  s = (a + b + c) / 2;
+            return Mathf.Sqrt(s * (s - a) * (s - b) * (s - c));
+        }
     }
+    public Float3 Midpoint => Float3.Average(a, b, c);
+    public float Perimeter => AB.Length + BC.Length + CA.Length;
+
+    public Line AB
+    {
+        get => (a, b);
+        set
+        {
+            a = value.a;
+            b = value.b;
+        }
+    }
+    public Line BC
+    {
+        get => (b, c);
+        set
+        {
+            b = value.a;
+            c = value.b;
+        }
+    }
+    public Line CA
+    {
+        get => (c, a);
+        set
+        {
+            c = value.a;
+            a = value.b;
+        }
+    }
+
+    public Float3 a, b, c;
+
+    public Triangle() : this(Float3.Zero, Float3.Zero, Float3.Zero) { }
+    public Triangle(Float3 a, Float3 b, Float3 c)
+    {
+        this.a = a;
+        this.b = b;
+        this.c = c;
+    }
+    public Triangle(Line ab, Line bc, Line ca)
+    {
+        if (ab.b != bc.a || bc.b != ca.a || ca.b != ab.a)
+            throw new DisconnectedLinesException(ab, bc, ca);
+
+        a = ab.a;
+        b = bc.a;
+        c = ca.a;
+    }
+    public Triangle(float x1, float y1, float x2, float y2, float x3, float y3)
+    {
+        a = (x1, y1, 0);
+        b = (x2, y2, 0);
+        c = (x3, y3, 0);
+    }
+    public Triangle(float x1, float y1, float z1, float x2, float y2, float z2, float x3,
+        float y3, float z3)
+    {
+        a = (x1, y1, z1);
+        b = (x2, y2, z2);
+        c = (x3, y3, z3);
+    }
+    public Triangle(Fill<Float3> fill) : this(fill(0), fill(1), fill(2)) { }
+    public Triangle(Fill<Int3> fill) : this(fill(0), fill(1), fill(2)) { }
+    public Triangle(Fill<float> fill) : this(fill(0), fill(1), fill(2), fill(3), fill(4),
+        fill(5), fill(6), fill(7), fill(8)) { }
+    public Triangle(Fill<int> fill) : this(fill(0), fill(1), fill(2), fill(3), fill(4),
+        fill(5), fill(6), fill(7), fill(8)) { }
+
+    public Float3 this[int index]
+    {
+        get => index switch
+        {
+            0 => a,
+            1 => b,
+            2 => c,
+            _ => throw new IndexOutOfRangeException(nameof(index)),
+        };
+        set
+        {
+            switch (index)
+            {
+                case 0:
+                    a = value;
+                    break;
+
+                case 1:
+                    b = value;
+                    break;
+
+                case 2:
+                    c = value;
+                    break;
+
+                default: throw new IndexOutOfRangeException(nameof(index));
+            }
+        }
+    }
+    public Float3 this[Index index]
+    {
+        get => this[index.IsFromEnd ? 3 - index.Value : index.Value];
+        set => this[index.IsFromEnd ? 3 - index.Value : index.Value] = value;
+    }
+    public Float3[] this[Range range]
+    {
+        get
+        {
+            int start = range.Start.IsFromEnd ? 3 - range.Start.Value : range.Start.Value;
+            int end = range.End.IsFromEnd ? 3 - range.End.Value : range.End.Value;
+            List<Float3> res = new();
+            for (int i = start; i < end; i++) res.Add(this[i]);
+            return res.ToArray();
+        }
+        set
+        {
+            int start = range.Start.IsFromEnd ? 3 - range.Start.Value : range.Start.Value;
+            int end = range.End.IsFromEnd ? 3 - range.End.Value : range.End.Value;
+            for (int i = start; i < end; i++) this[i] = value[i];
+        }
+    }
+
+    public Float3[] GetAllVerts() => new[] { a, b, c };
 }