diff --git a/cabecera.html b/cabecera.html
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+<!-- cabecera.html -->
+<nav class="navbar navbar-expand-lg navbar-kahoot py-3 mb-4">
+    <div class="container">
+        <a class="navbar-brand" href="index.php">
+            <img src="img/favicon/favicon.svg" alt="TRIVIAGMÁTICO" class="me-2" style="height: 35px;">
+            TRIVIAGMÁTICO
+        </a>
+
+        <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarContent">
+            <span class="navbar-toggler-icon"></span>
+        </button>
+
+        <div class="collapse navbar-collapse" id="navbarContent">
+            <ul class="navbar-nav me-auto mb-2 mb-lg-0"></ul>
+
+            <!-- Contenedor dinámico de usuario/botones -->
+            <div class="d-flex align-items-center gap-3" id="contenedorUsuarioCabecera"></div>
+        </div>
+    </div>
+</nav>
+
+<!-- MODAL DE LOGIN -->
+<div class="modal fade" id="modalLogin" tabindex="-1" aria-labelledby="loginModalLabel" aria-hidden="true">
+    <div class="modal-dialog modal-dialog-centered">
+        <div class="modal-content border-dark">
+            <div class="modal-header">
+                <h1 class="modal-title fs-5 fw-bold" id="loginModalLabel">
+                    <i class="fa-solid fa-right-to-bracket text-primary me-2"></i>Iniciar sesión
+                </h1>
+                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Cerrar"></button>
+            </div>
+            <div class="modal-body">
+                <form id="formLogin">
+                    <div class="form-floating mb-3">
+                        <input type="email" class="form-control border-dark" id="loginEmail" name="email" placeholder="Correo electrónico" required>
+                        <label for="loginEmail">Correo electrónico</label>
+                    </div>
+                    <div class="form-floating mb-3">
+                        <input type="password" class="form-control border-dark" id="loginPassword" name="contrasena" placeholder="Contraseña" required>
+                        <label for="loginPassword">Contraseña</label>
+                    </div>
+                    <div class="form-check">
+                        <input class="form-check-input" id="recordar" name="recordar" type="checkbox" />
+                        <label for="recordar" class="small">Recuérdeme durante 10 días</label>
+                    </div>
+                    <input type="hidden" name="orden" value="validar">
+                </form>
+                <div id="errorLogin" class="text-danger fw-bold mt-2"></div>
+            </div>
+            <div class="modal-footer">
+                <button type="button" class="btn btn-secondary rounded-pill px-3" data-bs-dismiss="modal">Cancelar</button>
+                <button type="button" class="btn btn-primary rounded-pill px-4" id="botonAceptarLogin">Entrar</button>
+            </div>
+        </div>
+    </div>
+</div>
+
+<!-- MODAL DE REGISTRO -->
+<div class="modal fade" id="modalRegistro" tabindex="-1" aria-labelledby="registroModalLabel" aria-hidden="true">
+    <div class="modal-dialog modal-dialog-centered">
+        <div class="modal-content border-dark">
+            <div class="modal-header">
+                <h1 class="modal-title fs-5 fw-bold" id="registroModalLabel">
+                    <i class="fa-solid fa-user-plus text-success me-2"></i>Registrarse
+                </h1>
+                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Cerrar"></button>
+            </div>
+            <div class="modal-body">
+                <form id="formRegistro">
+                    <div class="form-floating mb-3">
+                        <input type="text" class="form-control border-dark" id="regNombre" name="nombreUsuario" placeholder="Nombre" required>
+                        <label for="regNombre">Nombre</label>
+                    </div>
+                    <div class="form-floating mb-3">
+                        <input type="email" class="form-control border-dark" id="regEmail" name="email" placeholder="Correo electrónico" required>
+                        <label for="regEmail">Correo electrónico</label>
+                    </div>
+                    <div class="form-floating mb-3">
+                        <input type="password" class="form-control border-dark" id="regPassword" name="contrasena" placeholder="Contraseña" required>
+                        <label for="regPassword">Contraseña</label>
+                    </div>
+                    <div class="form-floating mb-3">
+                        <input type="password" class="form-control border-dark" id="regPasswordConfirm" name="contrasenaConfirm" placeholder="Confirmar contraseña" required>
+                        <label for="regPasswordConfirm">Confirmar contraseña</label>
+                    </div>
+                    <input type="hidden" name="orden" value="registrar">
+                </form>
+                <div id="errorRegistro" class="text-danger fw-bold mt-2"></div>
+            </div>
+            <div class="modal-footer">
+                <button type="button" class="btn btn-secondary rounded-pill px-3" data-bs-dismiss="modal">Cancelar</button>
+                <button type="button" class="btn btn-success rounded-pill px-4" id="botonAceptarRegistro">Registrarse</button>
+            </div>
+        </div>
+    </div>
+</div>
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