tMx/Content/Projectiles/MeteorHammerProjectile.cs

using tMx.Content.Items;
using Terraria;
using Terraria.ID;
using Terraria.ModLoader;
using System;
using Terraria.Audio;
using Microsoft.Xna.Framework;

namespace tMx.Content.Projectiles
{
    // This file showcases the concept of piercing.
    // The code of the item that spawns it is located at the bottom.

    // NPC.immune determines if an npc can be hit by a item or projectile owned by a particular player (it is an array, each slot corresponds to different players (whoAmI))
    // NPC.immune is decremented towards 0 every update
    // Melee items set NPC.immune to player.itemAnimation, which starts at item.useAnimation and decrements towards 0
    // Projectiles, however, provide mechanisms for custom immunity.
    // 1. penetrate == 1: A projectile with penetrate set to 1 in SetDefaults will hit regardless of the NPC's immunity counters (The penetrate from SetDefaults is remembered in maxPenetrate)
    //	Ex: Wooden Arrow.
    // 2. No code and penetrate > 1, penetrate == -1, or (appliesImmunityTimeOnSingleHits && penetrate == 1): npc.immune[owner] will be set to 10.
    // 	The NPC will be hit if not immune and will become immune to all damage for 10 ticks
    // 	Ex: Unholy Arrow
    // 3. Override OnHitNPC: If not immune, when it hits it manually set an immune other than 10
    // 	Ex: Arkhalis: Sets it to 5
    // 	Ex: Sharknado Minion: Sets to 20
    // 	Video: https://media-1.discordapp.net/attachments/242228770855976960/1150275205017636995/Projectile_Immunity_Sharknado_Arkhalis_Example.mp4 Notice how Sharknado minion hits prevent Arkhalis hits for a brief moment.
    // 4. Projectile.usesIDStaticNPCImmunity and Projectile.idStaticNPCHitCooldown: Specifies that a type of projectile has a shared immunity timer for each npc.
    // 	Use this if you want other projectiles a chance to damage, but don't want the same projectile type to hit an npc rapidly.
    // 	Ex: Ghastly Glaive is the only one who uses this.
    // 5. Projectile.usesLocalNPCImmunity and Projectile.localNPCHitCooldown: Specifies the projectile manages it's own immunity timers for each npc
    // 	Use this if you want the multiple projectiles of the same type to have a chance to attack rapidly, but don't want a single projectile to hit rapidly. A -1 value prevents the same projectile from ever hitting the npc again.
    // 	Ex: Lightning Aura sentries use this. (localNPCHitCooldown = 3, but other code controls how fast the projectile itself hits)
    // 		Overlapping Auras all have a chance to hit after each other even though they share the same ID.
    // Try the above by uncommenting out the respective bits of code in the projectile below.

    // This is a simple item that is based on the FlintlockPistol and shoots ExamplePiercingProjectile to showcase it.
    internal class MeteorHammerProjectile : ModProjectile
    {
        public override void SetDefaults()
        {
            Projectile.width = 8; // The width of projectile hitbox
            Projectile.height = 8; // The height of projectile hitbox
            Projectile.aiStyle = 1; // The ai style of the projectile, please reference the source code of Terraria
            Projectile.friendly = true; // Can the projectile deal damage to enemies?
            Projectile.hostile = false; // Can the projectile deal damage to the player?
            Projectile.DamageType = DamageClass.Melee; // Is the projectile shoot by a ranged weapon?
            Projectile.penetrate = 0; // How many monsters the projectile can penetrate. (OnTileCollide below also decrements penetrate for bounces as well)
            Projectile.timeLeft = 60; // The live time for the projectile (60 = 1 second, so 600 is 10 seconds)
            Projectile.alpha = 5; // The transparency of the projectile, 255 for completely transparent. (aiStyle 1 quickly fades the projectile in) Make sure to delete this if you aren't using an aiStyle that fades in. You'll wonder why your projectile is invisible.
            Projectile.light = 10.0f; // How much light emit around the projectile
            Projectile.ignoreWater = true; // Does the projectile's speed be influenced by water?
            Projectile.tileCollide = true; // Can the projectile collide with tiles?
            Projectile.extraUpdates = 1; // Set to above 0 if you want the projectile to update multiple time in a frame
        }

        public override bool OnTileCollide(Vector2 oldVelocity)
        {
            // If collide with tile, reduce the penetrate.
            // So the projectile can reflect at most 5 times
            Projectile.penetrate--;
            if (Projectile.penetrate <= 0)
            {
                Projectile.Kill();
            }
            else
            {
                Collision.HitTiles(Projectile.position, Projectile.velocity, Projectile.width, Projectile.height);
                SoundEngine.PlaySound(SoundID.Item10, Projectile.position);

                // If the projectile hits the left or right side of the tile, reverse the X velocity
                if (Math.Abs(Projectile.velocity.X - oldVelocity.X) > float.Epsilon)
                {
                    Projectile.velocity.X = -oldVelocity.X;
                }

                // If the projectile hits the top or bottom side of the tile, reverse the Y velocity
                if (Math.Abs(Projectile.velocity.Y - oldVelocity.Y) > float.Epsilon)
                {
                    Projectile.velocity.Y = -oldVelocity.Y;
                }
            }

            return false;
        }
    }
}