diff --git a/front_files/index.js b/front_files/index.js
index f7c3da1..13eebc3 100644
--- a/front_files/index.js
+++ b/front_files/index.js
@@ -1 +1,247 @@
-console.log("I actually wrote this!");
\ No newline at end of file
+console.log("Echo mock frontend loaded");
+
+(function () {
+  var createBtn = document.getElementById("create-session-btn");
+  var joinBtn = document.getElementById("join-session-btn");
+  var sessionIdInput = document.getElementById("session-id");
+
+  var landingCard = document.getElementById("landing-card");
+  var chatCard = document.getElementById("chat-card");
+  var chatLog = document.getElementById("chat-log");
+  var chatForm = document.getElementById("chat-form");
+  var chatInput = document.getElementById("chat-input");
+  var chatSendBtn = document.getElementById("chat-send-btn");
+  var leaveBtn = document.getElementById("leave-session-btn");
+  var sessionInfoEl = document.getElementById("chat-session-info");
+
+  if (
+    !createBtn ||
+    !joinBtn ||
+    !sessionIdInput ||
+    !landingCard ||
+    !chatCard ||
+    !chatLog ||
+    !chatForm ||
+    !chatInput ||
+    !chatSendBtn ||
+    !leaveBtn ||
+    !sessionInfoEl
+  ) {
+    console.warn("Echo UI elements not found, aborting mock init");
+    return;
+  }
+
+  var currentSessionId = null;
+  var currentParty = null; // "A" (offerer) or "B" (answerer)
+  var mockConnected = false;
+
+  function setSessionInfo(text) {
+    var partyLabel =
+      currentParty === "A"
+        ? "You are party A (offerer side)"
+        : currentParty === "B"
+        ? "You are party B (answerer side)"
+        : "";
+
+    sessionInfoEl.textContent = partyLabel
+      ? text + " · " + partyLabel
+      : text;
+  }
+
+  function appendMessage(kind, text) {
+    if (!chatLog) return;
+
+    var item = document.createElement("div");
+    item.classList.add("chat-message");
+
+    if (kind === "me") {
+      item.classList.add("me");
+    } else if (kind === "them") {
+      item.classList.add("them");
+    } else {
+      item.classList.add("system");
+    }
+
+    item.textContent = text;
+    chatLog.appendChild(item);
+    chatLog.scrollTop = chatLog.scrollHeight;
+  }
+
+  function setChatInputEnabled(enabled) {
+    chatInput.disabled = !enabled;
+    chatSendBtn.disabled = !enabled;
+  }
+
+  function resetState() {
+    currentSessionId = null;
+    currentParty = null;
+    mockConnected = false;
+    setChatInputEnabled(false);
+  }
+
+  function showLanding() {
+    landingCard.classList.remove("hidden");
+    chatCard.classList.add("hidden");
+    sessionIdInput.value = "";
+    resetState();
+  }
+
+  function showChat() {
+    landingCard.classList.add("hidden");
+    chatCard.classList.remove("hidden");
+    chatLog.innerHTML = "";
+    setChatInputEnabled(false);
+
+    if (!currentSessionId) {
+      return;
+    }
+
+    if (currentParty === "A") {
+      setSessionInfo(
+        "Session ID: " + currentSessionId + " (share this with your peer)"
+      );
+      appendMessage(
+        "system",
+        "Session created. TODO: open a WebSocket for signaling and send an SDP offer."
+      );
+    } else {
+      setSessionInfo("Joined session: " + currentSessionId);
+      appendMessage(
+        "system",
+        "Joined session. TODO: connect to the signaling WebSocket and respond with an SDP answer."
+      );
+    }
+
+    appendMessage(
+      "system",
+      "Mock mode: no real signaling or WebRTC yet. Everything stays local."
+    );
+  }
+
+  function mockConnectP2P() {
+    if (mockConnected) {
+      return;
+    }
+
+    mockConnected = true;
+    setChatInputEnabled(true);
+    appendMessage(
+      "system",
+      "Pretend the RTCDataChannel is open now. Replace this with real WebRTC events."
+    );
+  }
+
+  function sendChatMessage(text) {
+    if (!mockConnected) {
+      appendMessage(
+        "system",
+        "Mock mode: sending locally. Wire this up to RTCDataChannel.send()."
+      );
+    }
+
+    appendMessage("me", text);
+
+    if (!mockConnected) {
+      appendMessage(
+        "them",
+        "(Simulated peer) Replace with your RTCDataChannel onmessage handler."
+      );
+    }
+  }
+
+  async function createSession() {
+    if (createBtn.disabled) return;
+    createBtn.disabled = true;
+
+    try {
+      var response = await fetch("/api/session", {
+        method: "POST",
+        headers: { Accept: "application/json" },
+      });
+
+      if (!response.ok) {
+        throw new Error(
+          "Failed to create session (" + response.status + ")"
+        );
+      }
+
+      var data = await response.json();
+      if (!data || !data.sessionId) {
+        throw new Error("Session ID missing in response.");
+      }
+
+      currentSessionId = String(data.sessionId);
+      currentParty = "A";
+      showChat();
+
+      appendMessage(
+        "system",
+        "TODO: connect to /api/signal/session/" +
+          currentSessionId +
+          "/party/A via WebSocket."
+      );
+      mockConnectP2P();
+    } catch (err) {
+      console.error(err);
+      alert(err && err.message ? err.message : "Could not create session.");
+      resetState();
+    } finally {
+      createBtn.disabled = false;
+    }
+  }
+
+  function joinSession() {
+    var id = sessionIdInput.value.trim();
+    if (!id) {
+      sessionIdInput.focus();
+      return;
+    }
+
+    currentSessionId = id;
+    currentParty = "B";
+    showChat();
+
+    appendMessage(
+      "system",
+      "TODO: connect to /api/signal/session/" +
+        currentSessionId +
+        "/party/B via WebSocket."
+    );
+    mockConnectP2P();
+  }
+
+  createBtn.addEventListener("click", function () {
+    createSession();
+  });
+
+  joinBtn.addEventListener("click", function () {
+    joinSession();
+  });
+
+  sessionIdInput.addEventListener("keydown", function (event) {
+    if (event.key === "Enter") {
+      event.preventDefault();
+      joinSession();
+    }
+  });
+
+  chatForm.addEventListener("submit", function (event) {
+    event.preventDefault();
+
+    var text = chatInput.value.trim();
+    if (!text) {
+      return;
+    }
+
+    sendChatMessage(text);
+    chatInput.value = "";
+    chatInput.focus();
+  });
+
+  leaveBtn.addEventListener("click", function () {
+    showLanding();
+  });
+
+  // Initial state
+  setChatInputEnabled(false);
+})();