diff --git a/mods/periodic_and_more.js b/mods/periodic_and_more.js
new file mode 100644
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--- /dev/null
+++ b/mods/periodic_and_more.js
@@ -0,0 +1,81 @@
+// This is how to add a new mod to the game.
+
+// Create a new Javascript file like this one.
+// Add the file to the mods folder on GitHub, or host it somewhere else.
+// https://github.com/R74nCom/sandboxels/tree/main/mods
+
+// To add it in the Mod Loader:
+// If it is in the mods folder, you can just use the name of the file.
+// If it is hosted somewhere else, you can use the full URL, including the HTTPS://.
+
+// Adding elements:
+elements.mayo = {
+    color: "#ffffff",
+    behavior: behaviors.LIQUID,
+    category: "liquids",
+    viscosity: 100000,
+    state: "liquid",
+    density: 720,
+};
+
+// Changing existing elements:
+elements.water.color = "#ff0000";
+elements.water.behavior = behaviors.WALL;
+
+// Removing elements:
+// Be aware, things may break
+delete elements.ketchup;
+
+// Adding behavior presets:
+behaviors.SELFDELETE = [
+    "XX|XX|XX",
+    "XX|DL|XX",
+    "XX|XX|XX",
+];
+
+// Raw JavaScript behaviors:
+behaviors.mud.tick = function(pixel) {
+    if (tryMove(pixel, pixel.x, pixel.y+1)) {
+        console.log("Moved!");
+    }
+    else {
+        console.log("Couldn't move!")
+    }
+};
+
+// Create a new tool:
+elements.sand_exploder = {
+    color: "#ff0000",
+    tool: function(pixel) {
+        if (pixel.element == "sand") {
+            pixel.element = "explosion"
+        }
+    },
+    category: "tools",
+};
+
+// Add reactions to existing elements
+if (!elements.water.reactions) { // Include this block once
+    elements.water.reactions = {} // This creates the property if it doesn't exist
+}
+elements.water.reactions.mayo = { "elem1":null, "elem2":"mayo_water" }
+elements.water.reactions.soap = { "elem1":null, "elem2":"soapy_water" }
+
+// Run after all mods are loaded, for cross-mod compatibility
+runAfterLoad(function() {
+    // Your code here
+    console.log("Hello World!");
+});
+
+// Run if another mod is active
+if (enabledMods.includes("mods/test.js")) {
+    runAfterLoad(function() {
+        // Your code here
+        console.log("Hello World!");
+    });
+}
+
+// Creating eLists:
+eLists.PERIODIC = ["beryllium", "scandium", "vanadium", "manganese", "cobalt"];
+// Adding elements to eLists:
+eLists.CONDIMENT.push("honey");