Example Worm Code

using System;
using Microsoft.Xna.Framework;
using Terraria;
using Terraria.ModLoader;
using Terraria.ID;
namespace ExampleMod.NPCs
{
	//ported from my tAPI mod because I'm lazy
	public abstract class Worm : ModNPC
	{
		/* ai[0] = follower
		 * ai[1] = following
		 * ai[2] = distanceFromTail
		 * ai[3] = head
		 */
		public bool head;
		public bool tail;
		public int minLength;
		public int maxLength;
		public int headType;
		public int bodyType;
		public int tailType;
		public bool flies = false;
		public bool directional = false;
		public float speed;
		public float turnSpeed;

		public override void AI()
		{
			if (npc.localAI[1] == 0f)
			{
				npc.localAI[1] = 1f;
				Init();
			}
			if (npc.ai[3] > 0f)
			{
				npc.realLife = (int)npc.ai[3];
			}
			if (!head && npc.timeLeft < 300)
			{
				npc.timeLeft = 300;
			}
			if (npc.target < 0 || npc.target == 255 || Main.player[npc.target].dead)
			{				npc.TargetClosest(true);
			}
			if (Main.player[npc.target].dead && npc.timeLeft > 300)
			{
				npc.timeLeft = 300;
			}
			if (Main.netMode != 1)
			{
				if (!tail && npc.ai[0] == 0f)
				{
					if (head)
					{
						npc.ai[3] = (float)npc.whoAmI;
						npc.realLife = npc.whoAmI;
						npc.ai[2] = (float)Main.rand.Next(minLength, maxLength + 1);
						npc.ai[0] = (float)NPC.NewNPC((int)(npc.position.X + (float)(npc.width / 2)), (int)(npc.position.Y +(float)npc.height), bodyType, npc.whoAmI);
					}
					else if (npc.ai[2] > 0f)
					{
						npc.ai[0] = (float)NPC.NewNPC((int)(npc.position.X + (float)(npc.width / 2)), (int)(npc.position.Y +(float)npc.height), npc.type, npc.whoAmI);
					}
					else

					{
					npc.ai[0] = (float)NPC.NewNPC((int)(npc.position.X + (float)(npc.width / 2)), (int)(npc.position.Y + (float)npc.height), tailType, npc.whoAmI);
					}
					Main.npc[(int)npc.ai[0]].ai[3] = npc.ai[3];
					Main.npc[(int)npc.ai[0]].realLife = npc.realLife;
				Main.npc[(int)npc.ai[0]].ai[1] = (float)npc.whoAmI;
					Main.npc[(int)npc.ai[0]].ai[2] = npc.ai[2] - 1f;
					npc.netUpdate = true;
				}
			if (!head && (!Main.npc[(int)npc.ai[1]].active || (Main.npc[(int)npc.ai[1]].type != headType && Main.npc[(int)npc.ai[1]].type != bodyType)))
				{
					npc.life = 0;
					npc.HitEffect(0, 10.0);
					npc.active = false;
				}
			if (!tail && (!Main.npc[(int)npc.ai[0]].active || (Main.npc[(int)npc.ai[0]].type != bodyType && Main.npc[(int)npc.ai[0]].type != tailType)))
				{
					npc.life = 0;
					npc.HitEffect(0, 10.0);
					npc.active = false;
				}
				if (!npc.active && Main.netMode == 2)
				{
				NetMessage.SendData(28, -1, -1, "", npc.whoAmI, -1f, 0f, 0f, 0, 0, 0);
				}
			}
			int num180 = (int)(npc.position.X / 16f) - 1;
			int num181 = (int)((npc.position.X + (float)npc.width) / 16f) + 2;
			int num182 = (int)(npc.position.Y / 16f) - 1;
		int num183 = (int)((npc.position.Y + (float)npc.height) / 16f) + 2;
			if (num180 < 0)
			{
				num180 = 0;
			}
			if (num181 > Main.maxTilesX)
			{
				num181 = Main.maxTilesX;
			}
			if (num182 < 0)
			{
				num182 = 0;
			}
			if (num183 > Main.maxTilesY)
			{
				num183 = Main.maxTilesY;
			}
		bool flag18 = flies;

			if (!flag18)
			{
				for (int num184 = num180; num184 < num181; num184++)
				{
					for (int num185 = num182; num185 < num183; num185++)
					{
					if (Main.tile[num184, num185] != null && ((Main.tile[num184, num185].nactive() && (Mai.tileSolid[(int)Main.tile[num184, num185].type] || (Main.tileSolidTop[(int)Main.tile[num184, num185].type] && Main.tile[num184, num185].frameY == 0))) || Main.tile[num184, num185].liquid > 64))
						{
							Vector2 vector17;
							vector17.X = (float)(num184 * 16);
							vector17.Y = (float)(num185 * 16);
						if (npc.position.X + (float)npc.width > vector17.X && npc.position.X < vector17.X + 16f && npc.position.Y + (float)npc.height > vector17.Y && npc.position.Y < vector17.Y + 16f)
							{
								flag18 = true;
								if (Main.rand.Next(100) == 0 && npc.behindTiles && Main.tile[num184, num185].nactive())
								{
									WorldGen.KillTile(num184, num185, true, true, false);
								}
								if (Main.netMode != 1 && Main.tile[num184, num185].type == 2)
								{
									ushort arg_BFCA_0 = Main.tile[num184, num185 - 1].type;
								}
							}
						}
					}
				}
			}
		if (!flag18 && head)
			{
				Rectangle rectangle = new Rectangle((int)npc.position.X, (int)npc.position.Y, npc.width, npc.height);
				int num186 = 1000;
				bool flag19 = true;
				for (int num187 = 0; num187 < 255; num187++)
				{
					if (Main.player[num187].active)
					{
					Rectangle rectangle2 = new Rectangle((int)Main.player[num187].position.X - num186, (int)Main.player[num187].position.Y - num186, num186 * 2, num186 * 2);
						if (rectangle.Intersects(rectangle2))
						{
							flag19 = false;
							break;
						}
					}
				}
				if (flag19)
				{
					flag18 = true;
				}
			}
			if (directional)
			{
				if (npc.velocity.X < 0f)
				{
					npc.spriteDirection = 1;
				}
			else if (npc.velocity.X > 0f)
				{
					npc.spriteDirection = -1;
				}
			}
			float num188 = speed;
			float num189 = turnSpeed;
			Vector2 vector18 = new Vector2(npc.position.X + (float)npc.width * 0.5f, npc.position.Y + (float)npc.height * 0.5f);
			float num191 = Main.player[npc.target].position.X + (float)(Main.player[npc.target].width / 2);
			float num192 = Main.player[npc.target].position.Y + (float)(Main.player[npc.target].height / 2);
		num191 = (float)((int)(num191 / 16f) * 16);
			num192 = (float)((int)(num192 / 16f) * 16);
			vector18.X = (float)((int)(vector18.X / 16f) * 16);
			vector18.Y = (float)((int)(vector18.Y / 16f) * 16);
			num191 -= vector18.X;
			num192 -= vector18.Y;
			float num193 = (float)System.Math.Sqrt((double)(num191 * num191 + num192 * num192));
			if (npc.ai[1] > 0f && npc.ai[1] < (float)Main.npc.Length)
			{
				try
				{
					vector18 = new Vector2(npc.position.X + (float)npc.width * 0.5f, npc.position.Y + (float)npc.height * 0.5f);
					num191 = Main.npc[(int)npc.ai[1]].position.X + (float)(Main.npc[(int)npc.ai[1]].width / 2) - vector18.X;
					num192 = Main.npc[(int)npc.ai[1]].position.Y + (float)(Main.npc[(int)npc.ai[1]].height / 2) - vector18.Y;
				}
				catch
				{
				}
				npc.rotation = (float)System.Math.Atan2((double)num192, (double)num191) + 1.57f;
				num193 = (float)System.Math.Sqrt((double)(num191 * num191 + num192 * num192));
				int num194 = npc.width;
				num193 = (num193 - (float)num194) / num193;
				num191 *= num193;
				num192 *= num193;
				npc.velocity = Vector2.Zero;
				npc.position.X = npc.position.X + num191;
				npc.position.Y = npc.position.Y + num192;
				if (directional)
				{
					if (num191 < 0f)
					{
						npc.spriteDirection = 1;
					}
					if (num191 > 0f)
					{
						npc.spriteDirection = -1;
					}
				}
			}
			else
			{
				if (!flag18)
				{
					npc.TargetClosest(true);
					npc.velocity.Y = npc.velocity.Y + 0.11f;
					if (npc.velocity.Y > num188)
					{
						npc.velocity.Y = num188;
					}
					if ((double)(System.Math.Abs(npc.velocity.X) + System.Math.Abs(npc.velocity.Y)) < (double)num188 * 0.4)
					{
						if (npc.velocity.X < 0f)
						{
							npc.velocity.X = npc.velocity.X - num189 * 1.1f;
						}
						else
						{
							npc.velocity.X = npc.velocity.X + num189 * 1.1f;
						}
					}
					else if (npc.velocity.Y == num188)
					{
						if (npc.velocity.X < num191)
						{
							npc.velocity.X = npc.velocity.X + num189;
						}
						else if (npc.velocity.X > num191)
						{
							npc.velocity.X = npc.velocity.X - num189;
						}
					}
					else if (npc.velocity.Y > 4f)
					{
						if (npc.velocity.X < 0f)
						{
							npc.velocity.X = npc.velocity.X + num189 * 0.9f;
						}
						else
						{
							npc.velocity.X = npc.velocity.X - num189 * 0.9f;
						}
					}
				}
				else
				{
					if (!flies && npc.behindTiles && npc.soundDelay == 0)
					{
						float num195 = num193 / 40f;
						if (num195 < 10f)
						{
							num195 = 10f;
						}
						if (num195 > 20f)
						{
							num195 = 20f;
						}
						npc.soundDelay = (int)num195;
						Main.PlaySound(SoundID.Roar, npc.position, 1);
					}
					num193 = (float)System.Math.Sqrt((double)(num191 * num191 + num192 * num192));
					float num196 = System.Math.Abs(num191);
					float num197 = System.Math.Abs(num192);
					float num198 = num188 / num193;
					num191 *= num198;
					num192 *= num198;
					if (ShouldRun())
					{
						bool flag20 = true;
						for (int num199 = 0; num199 < 255; num199++)
						{
							if (Main.player[num199].active && !Main.player[num199].dead && Main.player[num199].ZoneCorrupt)
							{
								flag20 = false;
							}
						}
						if (flag20)
						{
							if (Main.netMode != 1 && (double)(npc.position.Y / 16f) > (Main.rockLayer + (double)Main.maxTilesY) / 2.0)
							{
								npc.active = false;
								int num200 = (int)npc.ai[0];
								while (num200 > 0 && num200 < 200 && Main.npc[num200].active && Main.npc[num200].aiStyle == npc.iStyle)
								{
									int num201 = (int)Main.npc[num200].ai[0];
									Main.npc[num200].active = false;
									npc.life = 0;
									if (Main.netMode == 2)
									{
										NetMessage.SendData(23, -1, -1, "", num200, 0f, 0f, 0f, 0, 0, 0);
									}
									num200 = num201;
								}
								if (Main.netMode == 2)
								{
									NetMessage.SendData(23, -1, -1, "", npc.whoAmI, 0f, 0f, 0f, 0, 0, 0);
								}
							}
							num191 = 0f;
							num192 = num188;
						}
					}
					bool flag21 = false;
					if (npc.type == 87)
					{
					if (((npc.velocity.X > 0f && num191 < 0f) || (npc.velocity.X < 0f && num191 > 0f) || (npc.velocity.Y > 0f && num12 < 0f) || (npc.velocity.Y < 0f && num192 > 0f)) && System.Math.Abs(npc.velocity.X) + System.Math.Abs(npc.velocity.Y) > num189 / 2f && num193 < 300f)
						{
							flag21 = true;
							if (System.Math.Abs(npc.velocity.X) + System.Math.Abs(npc.velocity.Y) < num188)
							{
								npc.velocity *= 1.1f;
							}
						}
					if (npc.position.Y > Main.player[npc.target].position.Y || (double)(Main.player[npc.target].position.Y / 16f) > Main.worldSurface || Main.player[npc.target].dead)
						{
							flag21 = true;
							if (System.Math.Abs(npc.velocity.X) < num188 / 2f)
							{
								if (npc.velocity.X == 0f)
								{
									npc.velocity.X = npc.velocity.X - (float)npc.direction;
								}
								npc.velocity.X = npc.velocity.X * 1.1f;
							}
							else
							{
								if (npc.velocity.Y > -num188)
								{
									npc.velocity.Y = npc.velocity.Y - num189;
								}
							}
						}
					}
					if (!flag21)
					{
					if ((npc.velocity.X > 0f && num191 > 0f) || (npc.velocity.X < 0f && num191 < 0f) || (npc.velocity.Y > 0f && num192 > 0f) || (npc.velocity.Y < 0f && num192 < 0f))
						{
							if (npc.velocity.X < num191)
							{
								npc.velocity.X = npc.velocity.X + num189;
							}
							else
							{
								if (npc.velocity.X > num191)
								{
								npc.velocity.X = npc.velocity.X - num189;

								}
							}
							if (npc.velocity.Y < num192)
							{
								npc.velocity.Y = npc.velocity.Y + num189;
							}
							else
							{
								if (npc.velocity.Y > num192)
								{
									npc.velocity.Y = npc.velocity.Y - num189;
								}
							}
						if ((double)System.Math.Abs(num192) < (double)num188 * 0.2 && ((npc.velocity.X > 0f && num191 < 0f) || (npc.velocity.X < 0f && num191 > 0f)))
						{
							if (npc.velocity.Y > 0f)
								{
									npc.velocity.Y = npc.velocity.Y + num189 * 2f;
								}
								else
								{
									npc.velocity.Y = npc.velocity.Y - num189 * 2f;
								}
							}
						if ((double)System.Math.Abs(num191) < (double)num188 * 0.2 && ((npc.velocity.Y > 0f && num192 < 0f) || (npc.velocity.Y < 0f && num192 > 0f)))
							{
								if (npc.velocity.X > 0f)
								{
									npc.velocity.X = npc.velocity.X + num189 * 2f;
								}
								else
								{
									npc.velocity.X = npc.velocity.X - num189 * 2f;
								}
							}
						}
						else
						{
							if (num196 > num197)
							{
								if (npc.velocity.X < num191)
								{
								npc.velocity.X = npc.velocity.X + num189 * 1.1f;
								}
								else if (npc.velocity.X > num191)
								{
									npc.velocity.X = npc.velocity.X - num189 * 1.1f;
								}
								if ((double)(System.Math.Abs(npc.velocity.X) + System.Math.Abs(npc.velocity.Y)) < (double)num188 * 0.5)
								{
									if (npc.velocity.Y > 0f)
									{
										npc.velocity.Y = npc.velocity.Y + num189;
									}
									else
									{
										npc.velocity.Y = npc.velocity.Y - num189;
									}
								}
							}
							else
							{
								if (npc.velocity.Y < num192)
								{
									npc.velocity.Y = npc.velocity.Y + num189 * 1.1f;
								}
								else if (npc.velocity.Y > num192)
								{
									npc.velocity.Y = npc.velocity.Y - num189 * 1.1f;
								}
								if ((double)(System.Math.Abs(npc.velocity.X) + System.Math.Abs(npc.velocity.Y)) < (double)num188 * 0.5)
								{
									if (npc.velocity.X > 0f)
									{
										npc.velocity.X = npc.velocity.X + num189;
									}
									else
									{
										npc.velocity.X = npc.velocity.X - num189;
									}
								}
							}
						}
					}
				}
				npc.rotation = (float)System.Math.Atan2((double)npc.velocity.Y, (double)npc.velocity.X) + 1.57f;
				if (head)
				{
					if (flag18)
					{
						if (npc.localAI[0] != 1f)
						{
							npc.netUpdate = true;
						}
						npc.localAI[0] = 1f;
					}
					else
					{
						if (npc.localAI[0] != 0f)
						{
							npc.netUpdate = true;
						}
						npc.localAI[0] = 0f;
					}
				if (((npc.velocity.X > 0f && npc.oldVelocity.X < 0f) || (npc.velocity.X < 0f && npc.oldVelocity.X > 0f) || (npc.velocity.Y > 0f && npc.oldVelocity.Y < 0f) || (npc.velocity.Y < 0f && npc.oldVelocity.Y > 0f)) && !npc.justHit)
					{
						npc.netUpdate = true;
						return;
					}
				}
			}
			CustomBehavior();
	}

		public virtual void Init()
		{
	}

		public virtual bool ShouldRun()
	{
			return false;
	}

		public virtual void CustomBehavior()
		{
		}
	}
}