diff --git a/src/App.tsx b/src/App.tsx
index df2d563..ff2b3ab 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -6,7 +6,8 @@ import CreateUser from './routes/CreateUser'
 import PostDetail from './routes/PostDetail'
 import Navbar from './components/Navbar'
 import CreatePostModal from './components/CreatePostModal'
-import PDFModal from './components/PDFModal'
+import MarkdownModal from './components/MarkdownModal'
+import NotificationCenter from './components/NotificationCenter'
 import useAppStore from './store/useAppStore'
 
 const App: React.FC = () => {
@@ -20,8 +21,9 @@ const App: React.FC = () => {
       <div className="nav">
         <Navbar />
       </div>
+      <NotificationCenter />
       <CreatePostModal />
-      <PDFModal />
+      <MarkdownModal />
       <main>
         <Routes>
           <Route path="/" element={<Home />} />
diff --git a/src/components/CreatePostModal.tsx b/src/components/CreatePostModal.tsx
index 4eebfc4..646ff5e 100644
--- a/src/components/CreatePostModal.tsx
+++ b/src/components/CreatePostModal.tsx
@@ -1,5 +1,7 @@
 import React, { useState, startTransition } from 'react'
 import useAppStore from '../store/useAppStore'
+import { generateRandomMarkdown } from '../utils/fileHelpers'
+import MarkdownPreview from './MarkdownPreview'
 
 const CreatePostModal: React.FC = () => {
   const isOpen = useAppStore((s) => s.ui.isCreatePostOpen)
@@ -8,28 +10,32 @@ const CreatePostModal: React.FC = () => {
   const createPost = useAppStore((s) => s.createPost)
 
   const [content, setContent] = useState('')
-  const [file, setFile] = useState<File | null>(null)
+  const [attachedMarkdown, setAttachedMarkdown] = useState<{name:string,content:string} | null>(null)
   const [error, setError] = useState<string | null>(null)
 
   if (!isOpen) return null
 
+  const onGenerate = () => {
+    const md = generateRandomMarkdown()
+    setAttachedMarkdown(md)
+  }
+
   const onSubmit = (e: React.FormEvent) => {
     e.preventDefault()
     if (!currentUserId) {
       setError('Select a user first')
       return
     }
-    if (!content.trim()) {
-      setError('Content required')
+    if (!content.trim() && !attachedMarkdown) {
+      setError('Content or markdown required')
       return
     }
     setError(null)
     startTransition(() => {
-      const attachedPDF = file ? { name: file.name, url: URL.createObjectURL(file) } : undefined
-      createPost({ authorId: currentUserId, content: content.trim(), attachedPDF })
+      createPost({ authorId: currentUserId, content: content.trim(), attachedMarkdown: attachedMarkdown ?? undefined })
       toggle()
       setContent('')
-      setFile(null)
+      setAttachedMarkdown(null)
     })
   }
 
@@ -40,14 +46,8 @@ const CreatePostModal: React.FC = () => {
         <form onSubmit={onSubmit}>
           <textarea className="textarea" value={content} onChange={(e) => setContent(e.target.value)} />
           <div style={{marginTop:8}}>
-            <input type="file" accept="application/pdf" onChange={(e) => {
-              const f = e.target.files && e.target.files[0]
-              if (f && f.type !== 'application/pdf') {
-                setError('Only PDF files allowed')
-                return
-              }
-              setFile(f ?? null)
-            }} />
+            <button type="button" className="button" onClick={onGenerate}>Generate Markdown</button>
+            {attachedMarkdown && <div style={{marginTop:8}}><MarkdownPreview content={attachedMarkdown.content} /></div>}
           </div>
           {error && <div style={{color:'red'}}>{error}</div>}
           <div style={{marginTop:8,display:'flex',justifyContent:'flex-end',gap:8}}>
diff --git a/src/components/MarkdownModal.tsx b/src/components/MarkdownModal.tsx
new file mode 100644
index 0000000..efd5a6f
--- /dev/null
+++ b/src/components/MarkdownModal.tsx
@@ -0,0 +1,27 @@
+import React from 'react'
+import useAppStore from '../store/useAppStore'
+import MarkdownPreview from './MarkdownPreview'
+
+const MarkdownModal: React.FC = () => {
+  const selectedPostId = useAppStore((s) => s.selectedPostId)
+  const setSelectedPost = useAppStore((s) => s.setSelectedPost)
+  const post = useAppStore((s) => s.posts.find((p) => p.id === selectedPostId))
+
+  if (!selectedPostId || !post?.attachedMarkdown) return null
+
+  return (
+    <div className="modal-backdrop" onClick={() => setSelectedPost(null)}>
+      <div className="modal" onClick={(e) => e.stopPropagation()}>
+        <div style={{display:'flex',justifyContent:'space-between',alignItems:'center'}}>
+          <h3>{post.attachedMarkdown.name}</h3>
+          <button onClick={() => setSelectedPost(null)}>Close</button>
+        </div>
+        <div style={{marginTop:8}}>
+          <MarkdownPreview content={post.attachedMarkdown.content} />
+        </div>
+      </div>
+    </div>
+  )
+}
+
+export default MarkdownModal
diff --git a/src/components/MarkdownPreview.tsx b/src/components/MarkdownPreview.tsx
new file mode 100644
index 0000000..45e1e13
--- /dev/null
+++ b/src/components/MarkdownPreview.tsx
@@ -0,0 +1,32 @@
+import React, { useMemo } from 'react'
+
+const renderMarkdown = (md: string) => {
+  if (!md) return ''
+  let html = md
+  // code blocks
+  html = html.replace(/```([\s\S]*?)```/g, '<pre><code>$1</code></pre>')
+  // headings
+  html = html.replace(/^### (.*$)/gim, '<h3>$1</h3>')
+  html = html.replace(/^## (.*$)/gim, '<h2>$1</h2>')
+  html = html.replace(/^# (.*$)/gim, '<h1>$1</h1>')
+  // bold / italics
+  html = html.replace(/\*\*(.*?)\*\*/g, '<strong>$1</strong>')
+  html = html.replace(/\*(.*?)\*/g, '<em>$1</em>')
+  // links
+  html = html.replace(/\[([^\]]+)\]\(([^)]+)\)/g, '<a href="$2" target="_blank" rel="noreferrer">$1</a>')
+  // lists
+  html = html.replace(/^\s*-\s+(.*)$/gim, '<li>$1</li>')
+  // wrap list items
+  html = html.replace(/(<li>[\s\S]*?<\/li>)/gms, '<ul>$1</ul>')
+  // paragraphs
+  html = html.replace(/\n{2,}/g, '</p><p>')
+  html = `<p>${html}</p>`
+  return html
+}
+
+const MarkdownPreview: React.FC<{ content: string }> = ({ content }) => {
+  const html = useMemo(() => renderMarkdown(content), [content])
+  return <div className="markdown-preview" dangerouslySetInnerHTML={{ __html: html }} />
+}
+
+export default MarkdownPreview
diff --git a/src/components/NotificationCenter.tsx b/src/components/NotificationCenter.tsx
new file mode 100644
index 0000000..4481818
--- /dev/null
+++ b/src/components/NotificationCenter.tsx
@@ -0,0 +1,22 @@
+import React from 'react'
+import useAppStore from '../store/useAppStore'
+
+const NotificationCenter: React.FC = () => {
+  const notifications = useAppStore((s) => s.notifications)
+  const removeNotification = useAppStore((s) => s.removeNotification)
+
+  if (!notifications || notifications.length === 0) return null
+
+  return (
+    <div className="notif-container">
+      {notifications.map((n) => (
+        <div key={n.id} className={`notif ${n.type ?? ''}`}>
+          <div>{n.message}</div>
+          <button onClick={() => removeNotification(n.id)}>×</button>
+        </div>
+      ))}
+    </div>
+  )
+}
+
+export default NotificationCenter
diff --git a/src/components/PostCard.tsx b/src/components/PostCard.tsx
index 6c5d14e..c709123 100644
--- a/src/components/PostCard.tsx
+++ b/src/components/PostCard.tsx
@@ -1,46 +1,106 @@
-import React, { memo } from 'react'
+import React, { memo, useState } from 'react'
 import { Post } from '../types/Post'
 import useAppStore from '../store/useAppStore'
-import { Link } from 'react-router-dom'
-import { formatTime } from '../utils/fileHelpers'
-import PDFPreview from './PDFPreview'
+import { Link, useNavigate } from 'react-router-dom'
+import { formatTime, generateToken } from '../utils/fileHelpers'
+import MarkdownPreview from './MarkdownPreview'
 
 const PostCard: React.FC<{ post: Post }> = ({ post }) => {
   const author = useAppStore((s) => s.users.find((u) => u.id === post.authorId))
   const endorsePost = useAppStore((s) => s.endorsePost)
   const setSelectedPost = useAppStore((s) => s.setSelectedPost)
+  const currentUserId = useAppStore((s) => s.currentUserId)
+  const addNotification = useAppStore((s) => s.addNotification)
+  const navigate = useNavigate()
+
+  const [shareUrl, setShareUrl] = useState<string | null>(null)
+  const [copied, setCopied] = useState(false)
 
   if (!author) return null
 
+  const handleEndorse = async (e?: React.MouseEvent) => {
+    e?.stopPropagation()
+    if (!currentUserId) {
+      addNotification('Select a current user (top-right) to endorse from.', 'error')
+      return
+    }
+    if (currentUserId === post.authorId) {
+      addNotification("You can't endorse your own post.", 'error')
+      return
+    }
+    endorsePost(post.id)
+    const token = generateToken(6)
+    const url = `https://arxiv.org/auth/endorse?x=${token}`
+    setShareUrl(url)
+    try {
+      if (navigator.clipboard && navigator.clipboard.writeText) {
+        await navigator.clipboard.writeText(url)
+        setCopied(true)
+        addNotification('Share link copied to clipboard', 'success')
+      } else {
+        const area = document.createElement('textarea')
+        area.value = url
+        document.body.appendChild(area)
+        area.select()
+        document.execCommand('copy')
+        document.body.removeChild(area)
+        setCopied(true)
+        addNotification('Share link copied to clipboard', 'success')
+      }
+    } catch (e) {
+      console.error('copy failed', e)
+      addNotification('Could not copy share link', 'error')
+    }
+    setTimeout(() => setCopied(false), 2000)
+  }
+
+  const handleCopy = async (e?: React.MouseEvent) => {
+    e?.stopPropagation()
+    if (!shareUrl) return
+    try {
+      await navigator.clipboard.writeText(shareUrl)
+      setCopied(true)
+      addNotification('Share link copied to clipboard', 'success')
+      setTimeout(() => setCopied(false), 2000)
+    } catch {
+      addNotification('Could not copy share link', 'error')
+    }
+  }
+
   return (
-    <div className="card">
+    <div className="card post-card" onClick={() => navigate(`/post/${post.id}`)} style={{cursor:'pointer'}}>
       <div style={{display:'flex',justifyContent:'space-between'}}>
         <div>
-          <Link to={`/profile/${author.id}`}><strong>{author.name}</strong></Link>
+          <Link to={`/profile/${author.id}`} onClick={(e) => e.stopPropagation()}><strong>{author.name}</strong></Link>
           <div className="small">{formatTime(post.createdAt)} ago</div>
         </div>
-        <div style={{display:'flex',gap:6}}>
+        <div className="tags-row">
           {author.specialties.map((sp) => (
             <span key={sp} className="tag">{sp}</span>
           ))}
         </div>
       </div>
       <p style={{marginTop:8}}>{post.content}</p>
-      {post.attachedPDF && (
+      {post.attachedMarkdown && (
         <div style={{marginTop:8}}>
-          <div className="small">{post.attachedPDF.name}</div>
-          <div style={{marginTop:6,display:'flex',gap:8}}>
-            <button className="button" onClick={() => setSelectedPost(post.id)}>Open PDF</button>
-            <PDFPreview url={post.attachedPDF.url} name={post.attachedPDF.name} />
+          <div className="small">{post.attachedMarkdown.name}</div>
+          <div style={{marginTop:6}}>
+            <MarkdownPreview content={post.attachedMarkdown.content} />
           </div>
         </div>
       )}
       <div style={{display:'flex',justifyContent:'space-between',alignItems:'center',marginTop:8}}>
         <div>
-          <button className="button" onClick={() => endorsePost(post.id)}>Endorse Post ({post.endorsements})</button>
-          <Link to={`/post/${post.id}`} style={{marginLeft:8}}>View</Link>
+          <button className="button" onClick={(e) => { e.stopPropagation(); handleEndorse(e); }}>Endorse Post ({post.endorsements})</button>
+          <button className="button" style={{marginLeft:8}} onClick={(e) => { e.stopPropagation(); setSelectedPost(post.id); }}>Open MD</button>
         </div>
       </div>
+      {shareUrl && (
+        <div className="small" style={{marginTop:8}}>
+          Share link: <a href={shareUrl} target="_blank" rel="noreferrer" onClick={(e) => e.stopPropagation()}>{shareUrl}</a>
+          <button style={{marginLeft:8}} onClick={(e) => { e.stopPropagation(); handleCopy(e); }}>{copied ? 'Copied' : 'Copy'}</button>
+        </div>
+      )}
     </div>
   )
 }
diff --git a/src/components/UserCard.tsx b/src/components/UserCard.tsx
index 0d8958e..7a22c4c 100644
--- a/src/components/UserCard.tsx
+++ b/src/components/UserCard.tsx
@@ -1,13 +1,34 @@
 import React from 'react'
 import { User } from '../types/User'
 import { Link } from 'react-router-dom'
+import useAppStore from '../store/useAppStore'
 
 const UserCard: React.FC<{ user: User }> = ({ user }) => {
+  const currentUserId = useAppStore((s) => s.currentUserId)
+  const endorseUser = useAppStore((s) => s.endorseUser)
+  const addNotification = useAppStore((s) => s.addNotification)
+
+  const onEmailClick = (e: React.MouseEvent) => {
+    e.preventDefault()
+    if (!currentUserId) {
+      addNotification('Select a current user (top-right) to endorse from.', 'error')
+      return
+    }
+    if (currentUserId === user.id) {
+      addNotification("You can't endorse yourself.", 'error')
+      return
+    }
+    const specialty = user.specialties[0] ?? 'General'
+    endorseUser(user.id, specialty)
+    addNotification(`Endorsed ${user.name} for ${specialty}`, 'success')
+  }
+
   return (
     <div className="card">
       <Link to={`/profile/${user.id}`}><strong>{user.name}</strong></Link>
+      <div className="small"><a href="#" onClick={onEmailClick}>{user.email}</a></div>
       <div className="small">{user.bio}</div>
-      <div style={{marginTop:8}}>
+      <div className="tags-row" style={{marginTop:8}}>
         {user.specialties.map((s) => (
           <span key={s} className="tag">{s} ({user.endorsements[s] ?? 0})</span>
         ))}
diff --git a/src/index.css b/src/index.css
index 68388ba..29dce52 100644
--- a/src/index.css
+++ b/src/index.css
@@ -15,7 +15,7 @@ body{font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,'He
 .post-card{border-radius:14px;padding:14px}
 .post-thumbs .thumb{width:120px;height:84px;background:linear-gradient(180deg,#f8fafc,#eef2ff);border-radius:10px}
 .avatar{width:56px;height:56px;border-radius:999px;background:#e6f0ff;color:#1e40af;display:flex;align-items:center;justify-content:center;font-weight:600}
-.tag{display:inline-flex;align-items:center;justify-content:center;height:32px;min-width:32px;padding:0 14px;background:#eef2ff;color:#1e40af;border-radius:999px;font-size:12px;margin-right:8px;white-space:nowrap}
+.tag{display:inline-flex;align-items:center;justify-content:center;height:32px;min-width:32px;padding:0 14px;background:#eef2ff;color:#1e40af;border-radius:999px;font-size:12px;margin-right:0;white-space:nowrap}
 .button{background:#2563eb;color:#fff;border:none;padding:8px 12px;border-radius:6px;cursor:pointer}
 .small{font-size:13px;color:var(--muted)}
 .sidebar{width:300px}
@@ -24,3 +24,24 @@ body{font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,'He
 .textarea{width:100%;min-height:100px;padding:8px;border:1px solid #e5e7eb;border-radius:6px}
 .create-input{display:flex;flex-direction:column}
 .rec{width:64px;height:64px;border-radius:12px;background:#f8fafc;display:flex;align-items:center;justify-content:center}
+
+.markdown-preview{border:1px solid #eef2f6;padding:12px;border-radius:8px;background:#ffffff}
+
+/* Create account styles */
+.create-account-bg{background:linear-gradient(180deg,#00c6ff 0%,#0072ff 100%)}
+.create-card{width:420px;margin:60px auto;padding:32px;background:#fff;border-radius:8px;text-align:center;box-shadow:0 20px 40px rgba(2,6,23,0.12)}
+.create-card h2{font-size:28px;color:#1e3a8a;margin-bottom:18px}
+.input{width:100%;padding:12px;border-radius:6px;border:1px solid #eef2f6;margin-bottom:12px}
+.btn-gradient{background:linear-gradient(90deg,#0ea5e9,#60a5fa);color:#fff;padding:12px 24px;border-radius:999px;border:none;cursor:pointer}
+.btn-ghost{background:#f1f5f9;padding:12px 24px;border-radius:999px;border:none;color:#475569;margin-left:12px}
+
+/* Tags row spacing */
+.tags-row{display:flex;align-items:center;gap:5px;flex-wrap:wrap}
+
+/* Notifications */
+.notif-container{position:fixed;top:16px;right:16px;z-index:1000;display:flex;flex-direction:column;gap:8px}
+.notif{background:#0f172a;color:#fff;padding:10px 14px;border-radius:8px;box-shadow:0 8px 20px rgba(2,6,23,0.2);min-width:220px;display:flex;justify-content:space-between;align-items:center}
+.notif.success{background:#15803d}
+.notif.error{background:#b91c1c}
+.notif button{background:transparent;border:none;color:inherit;cursor:pointer;padding:6px}
+
diff --git a/src/mock/seedData.ts b/src/mock/seedData.ts
index dfbe95e..616a2b2 100644
--- a/src/mock/seedData.ts
+++ b/src/mock/seedData.ts
@@ -55,9 +55,9 @@ export const seedUsers = (): User[] => {
 }
 
 export const seedPosts = (users: User[]): Post[] => {
-  const samplePDF = 'https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf'
+  const sampleMarkdown = `# Sample Paper\n\nThis is a sample markdown abstract.\n\n## Methods\n- Step 1\n- Step 2\n\n## Conclusion\nThis is a short conclusion.`
   const posts: Post[] = [
-    { id: 'p1', authorId: users[0].id, content: 'Working on a new transformer variant.', attachedPDF: { name: 'paper.pdf', url: samplePDF }, endorsements: 2, createdAt: now - 1000 * 60 * 30 },
+    { id: 'p1', authorId: users[0].id, content: 'Working on a new transformer variant.', attachedMarkdown: { name: 'paper.md', content: sampleMarkdown }, endorsements: 2, createdAt: now - 1000 * 60 * 30 },
     { id: 'p2', authorId: users[1].id, content: 'New results on memory consolidation in models.', endorsements: 1, createdAt: now - 1000 * 60 * 60 * 2 },
     { id: 'p3', authorId: users[2].id, content: 'Dataset release for coastal temperature anomalies.', endorsements: 0, createdAt: now - 1000 * 60 * 60 * 5 },
     { id: 'p4', authorId: users[3].id, content: 'Simulations of topological phases.', endorsements: 3, createdAt: now - 1000 * 60 * 60 * 24 },
@@ -65,7 +65,7 @@ export const seedPosts = (users: User[]): Post[] => {
     { id: 'p6', authorId: users[0].id, content: 'Trying a new optimization schedule.', endorsements: 1, createdAt: now - 1000 * 60 * 60 * 3 },
     { id: 'p7', authorId: users[1].id, content: 'Open-source code for preprocessing.', endorsements: 2, createdAt: now - 1000 * 60 * 60 * 6 },
     { id: 'p8', authorId: users[2].id, content: 'Collaboration call on climate econometrics.', endorsements: 0, createdAt: now - 1000 * 60 * 60 * 12 },
-    { id: 'p9', authorId: users[3].id, content: 'Preprint draft available.', attachedPDF: { name: 'draft.pdf', url: samplePDF }, endorsements: 1, createdAt: now - 1000 * 60 * 60 * 48 },
+    { id: 'p9', authorId: users[3].id, content: 'Preprint draft available.', attachedMarkdown: { name: 'draft.md', content: sampleMarkdown }, endorsements: 1, createdAt: now - 1000 * 60 * 60 * 48 },
     { id: 'p10', authorId: users[4].id, content: 'Survey on lab replication practices.', endorsements: 0, createdAt: now - 1000 * 60 * 60 * 72 },
   ]
   return posts
diff --git a/src/routes/CreateUser.tsx b/src/routes/CreateUser.tsx
index f9f0ccf..50a07b3 100644
--- a/src/routes/CreateUser.tsx
+++ b/src/routes/CreateUser.tsx
@@ -5,42 +5,37 @@ import useAppStore from '../store/useAppStore'
 const CreateUser: React.FC = () => {
   const [name, setName] = useState('')
   const [email, setEmail] = useState('')
+  const [password, setPassword] = useState('')
   const [bio, setBio] = useState('')
   const [specialties, setSpecialties] = useState('')
   const createUser = useAppStore((s) => s.createUser)
+  const addNotification = useAppStore((s) => s.addNotification)
   const navigate = useNavigate()
 
   const onSubmit = (e: React.FormEvent) => {
     e.preventDefault()
     const parsed = specialties.split(',').map((s) => s.trim()).filter(Boolean)
-    if (!name || !email || !bio || parsed.length === 0) return alert('All fields required and at least one specialty')
+    if (!name || !email || !bio || parsed.length === 0) {
+      addNotification('All fields required and at least one specialty', 'error')
+      return
+    }
     const newUser = createUser({ name, email, bio, specialties: parsed })
     navigate(`/profile/${newUser.id}`)
   }
 
   return (
-    <div className="container">
-      <div className="card">
-        <h2>Create User</h2>
-        <form onSubmit={onSubmit}>
-          <div>
-            <label>Name</label>
-            <input value={name} onChange={(e) => setName(e.target.value)} />
-          </div>
-          <div>
-            <label>Email</label>
-            <input value={email} onChange={(e) => setEmail(e.target.value)} />
-          </div>
-          <div>
-            <label>Bio</label>
-            <input value={bio} onChange={(e) => setBio(e.target.value)} />
-          </div>
-          <div>
-            <label>Specialties (comma separated)</label>
-            <input value={specialties} onChange={(e) => setSpecialties(e.target.value)} />
-          </div>
-          <div style={{marginTop:8}}>
-            <button className="button" type="submit">Create</button>
+    <div className="create-account-bg" style={{minHeight:'100vh',display:'flex',alignItems:'center',justifyContent:'center'}}>
+      <div className="create-card">
+        <h2>Create Account</h2>
+        <form onSubmit={onSubmit} style={{display:'flex',flexDirection:'column',gap:12}}>
+          <input className="input" placeholder="Name" value={name} onChange={(e) => setName(e.target.value)} />
+          <input className="input" placeholder="E-mail" value={email} onChange={(e) => setEmail(e.target.value)} />
+          <input type="password" className="input" placeholder="Password" value={password} onChange={(e) => setPassword(e.target.value)} />
+          <textarea className="input" placeholder="Short bio" value={bio} onChange={(e) => setBio(e.target.value)} />
+          <input className="input" placeholder="Specialties (comma separated)" value={specialties} onChange={(e) => setSpecialties(e.target.value)} />
+          <div style={{display:'flex',justifyContent:'center',marginTop:8}}>
+            <button className="btn-gradient" type="submit">SIGN UP</button>
+            <button type="button" className="btn-ghost" onClick={() => navigate('/')}>SIGN IN</button>
           </div>
         </form>
       </div>
diff --git a/src/routes/Home.tsx b/src/routes/Home.tsx
index dff9fa5..1759b14 100644
--- a/src/routes/Home.tsx
+++ b/src/routes/Home.tsx
@@ -8,6 +8,8 @@ const Home: React.FC = () => {
   const currentUserId = useAppStore((s) => s.currentUserId)
   const suggestions = users.filter((u) => u.id !== currentUserId).slice(0, 3)
 
+  const toggleCreatePost = useAppStore((s) => s.toggleCreatePost)
+
   return (
     <div className="feed-shell">
       <div className="container main-card" style={{display:'flex',gap:20,alignItems:'flex-start'}}>
@@ -28,14 +30,15 @@ const Home: React.FC = () => {
             <div className="small">Recent · Friends · Popular</div>
           </header>
 
-          <Feed />
-
-          <div className="create-input card" style={{marginTop:12}}>
-            <input placeholder="Share something..." style={{width:'100%',border:'none',outline:'none'}} />
+          <div className="create-input card" style={{marginBottom:12}}>
+            <input placeholder="Share something..." style={{width:'100%',border:'none',outline:'none'}} onFocus={() => toggleCreatePost()} />
             <div style={{display:'flex',justifyContent:'flex-end',marginTop:8}}>
-              <button className="button">Send</button>
+              <button className="button" onClick={() => toggleCreatePost()}>Send</button>
             </div>
           </div>
+
+          <Feed />
+
         </main>
 
         <aside className="right-column">
diff --git a/src/routes/PostDetail.tsx b/src/routes/PostDetail.tsx
index 66f0058..0eea9a2 100644
--- a/src/routes/PostDetail.tsx
+++ b/src/routes/PostDetail.tsx
@@ -1,25 +1,74 @@
-import React from 'react'
-import { useParams } from 'react-router-dom'
+import React, { useState } from 'react'
+import { useParams, Link } from 'react-router-dom'
 import useAppStore from '../store/useAppStore'
-import PDFPreview from '../components/PDFPreview'
+import MarkdownPreview from '../components/MarkdownPreview'
+import { generateToken } from '../utils/fileHelpers'
 
 const PostDetail: React.FC = () => {
   const { id } = useParams<{ id: string }>()
   const post = useAppStore((s) => s.posts.find((p) => p.id === id))
   const author = useAppStore((s) => s.users.find((u) => u.id === post?.authorId))
   const endorsePost = useAppStore((s) => s.endorsePost)
+  const currentUserId = useAppStore((s) => s.currentUserId)
+  const addNotification = useAppStore((s) => s.addNotification)
+
+  const [shareUrl, setShareUrl] = useState<string | null>(null)
+  const [copied, setCopied] = useState(false)
 
   if (!post) return <div className="card">Post not found</div>
 
+  const handleEndorse = async () => {
+    if (!currentUserId) {
+      addNotification('Select a current user (top-right) to endorse from.', 'error')
+      return
+    }
+    if (currentUserId === post.authorId) {
+      addNotification("You can't endorse your own post.", 'error')
+      return
+    }
+    endorsePost(post.id)
+    const token = generateToken(6)
+    const url = `https://arxiv.org/auth/endorse?x=${token}`
+    setShareUrl(url)
+    try {
+      await navigator.clipboard.writeText(url)
+      setCopied(true)
+      addNotification('Share link copied to clipboard', 'success')
+    } catch {
+      // ignore
+    }
+  }
+
+  const handleCopy = async () => {
+    if (!shareUrl) return
+    try {
+      await navigator.clipboard.writeText(shareUrl)
+      setCopied(true)
+      setTimeout(() => setCopied(false), 2000)
+      addNotification('Share link copied to clipboard', 'success')
+    } catch {
+      addNotification('Could not copy share link', 'error')
+    }
+  }
+
   return (
     <div className="container">
+      <div style={{marginBottom:12}}>
+        <Link to="/">← Home</Link>
+      </div>
       <div className="card">
         <h3>{author?.name}</h3>
         <div className="small">{author?.bio}</div>
         <div style={{marginTop:8}}>{post.content}</div>
-        {post.attachedPDF && <PDFPreview url={post.attachedPDF.url} name={post.attachedPDF.name} />}
+        {post.attachedMarkdown && <MarkdownPreview content={post.attachedMarkdown.content} />}
         <div style={{marginTop:8}}>
-          <button className="button" onClick={() => endorsePost(post.id)}>Endorse Post ({post.endorsements})</button>
+          <button className="button" onClick={handleEndorse}>Endorse Post ({post.endorsements})</button>
+          {shareUrl && (
+            <div className="small" style={{marginTop:8}}>
+              Share link: <a href={shareUrl} target="_blank" rel="noreferrer">{shareUrl}</a>
+              <button style={{marginLeft:8}} onClick={handleCopy}>{copied ? 'Copied' : 'Copy'}</button>
+            </div>
+          )}
         </div>
       </div>
     </div>
diff --git a/src/routes/Profile.tsx b/src/routes/Profile.tsx
index 5e9d434..5c9552a 100644
--- a/src/routes/Profile.tsx
+++ b/src/routes/Profile.tsx
@@ -13,13 +13,30 @@ const Profile: React.FC = () => {
   const currentUserId = useAppStore((s) => s.currentUserId)
   const endorsementHistory = useAppStore((s) => s.endorsementHistory)
   const allUsers = useAppStore((s) => s.users)
+  const addNotification = useAppStore((s) => s.addNotification)
 
   if (!user) return <div className="card">User not found</div>
 
+  const onEmailClick = (e: React.MouseEvent) => {
+    e.preventDefault()
+    if (!currentUserId) {
+      addNotification('Select a current user (top-right) to endorse from.', 'error')
+      return
+    }
+    if (currentUserId === user.id) {
+      addNotification("You can't endorse yourself.", 'error')
+      return
+    }
+    const specialty = user.specialties[0] ?? 'General'
+    endorseUser(user.id, specialty)
+    addNotification(`Endorsed ${user.name} for ${specialty}`, 'success')
+  }
+
   return (
     <div className="container">
       <div className="card">
         <h2>{user.name}</h2>
+        <div className="small"><a href="#" onClick={onEmailClick}>{user.email}</a></div>
         <div className="small">{user.bio}</div>
         <div style={{marginTop:8}}>
           {user.specialties.map((s) => (
diff --git a/src/store/useAppStore.ts b/src/store/useAppStore.ts
index 3bd4fb1..ba4242a 100644
--- a/src/store/useAppStore.ts
+++ b/src/store/useAppStore.ts
@@ -5,22 +5,30 @@ import { seedUsers, seedPosts } from '../mock/seedData'
 
 type UIState = { isCreatePostOpen: boolean }
 
+type EndorsementHistoryItem = { id: string; type: 'user' | 'post'; by?: string | null; toUserId?: string; postId?: string; specialty?: string; createdAt: number }
+
+type Notification = { id: string; message: string; type?: 'success' | 'error' | 'info'; createdAt: number }
+
 type AppState = {
   users: User[]
   posts: Post[]
   currentUserId: string | null
   selectedPostId: string | null
   ui: UIState
-  endorsementHistory: { id: string; type: 'user' | 'post'; by?: string | null; toUserId?: string; postId?: string; specialty?: string; createdAt: number }[]
+  endorsementHistory: EndorsementHistoryItem[]
+  notifications: Notification[]
   seedData: () => void
   createUser: (data: { name: string; email: string; bio: string; specialties: string[] }) => User
   setCurrentUser: (id: string | null) => void
-  createPost: (data: { authorId: string; content: string; attachedPDF?: { name: string; url: string } }) => Post
+  createPost: (data: { authorId: string; content: string; attachedMarkdown?: { name: string; content: string } }) => Post
   endorseUser: (userId: string, specialty: string) => void
   endorsePost: (postId: string) => void
   attachPDFToPost: (postId: string, file: File) => void
+  attachMarkdownToPost: (postId: string, md: { name: string; content: string }) => void
   setSelectedPost: (id: string | null) => void
   toggleCreatePost: () => void
+  addNotification: (message: string, type?: 'success' | 'error' | 'info', duration?: number) => void
+  removeNotification: (id: string) => void
 }
 
 const makeId = () => (typeof crypto !== 'undefined' && 'randomUUID' in crypto ? (crypto as any).randomUUID() : 'id-' + Date.now())
@@ -32,6 +40,7 @@ const useAppStore = create<AppState>((set, get) => ({
   selectedPostId: null,
   ui: { isCreatePostOpen: false },
   endorsementHistory: [],
+  notifications: [],
 
   seedData: () => {
     const users = seedUsers()
@@ -62,7 +71,7 @@ const useAppStore = create<AppState>((set, get) => ({
       id,
       authorId: data.authorId,
       content: data.content,
-      attachedPDF: data.attachedPDF,
+      attachedMarkdown: data.attachedMarkdown,
       endorsements: 0,
       createdAt: Date.now(),
     }
@@ -83,7 +92,6 @@ const useAppStore = create<AppState>((set, get) => ({
     }))
   },
 
-
   endorsePost: (postId) => {
     const by = get().currentUserId ?? null
     set((state) => ({
@@ -92,7 +100,6 @@ const useAppStore = create<AppState>((set, get) => ({
     }))
   },
 
-
   attachPDFToPost: (postId, file) => {
     const url = URL.createObjectURL(file)
     set((state) => ({
@@ -100,9 +107,26 @@ const useAppStore = create<AppState>((set, get) => ({
     }))
   },
 
+  attachMarkdownToPost: (postId, md) => {
+    set((state) => ({
+      posts: state.posts.map((p) => (p.id === postId ? { ...p, attachedMarkdown: md } : p)),
+    }))
+  },
+
   setSelectedPost: (id) => set(() => ({ selectedPostId: id })),
 
   toggleCreatePost: () => set((state) => ({ ui: { isCreatePostOpen: !state.ui.isCreatePostOpen } })),
+
+  addNotification: (message, type = 'info', duration = 4000) => {
+    const id = makeId()
+    const notif = { id, message, type, createdAt: Date.now() }
+    set((state) => ({ notifications: [notif, ...(state.notifications || [])] }))
+    setTimeout(() => {
+      set((state) => ({ notifications: (state.notifications || []).filter((n) => n.id !== id) }))
+    }, duration)
+  },
+
+  removeNotification: (id) => set((state) => ({ notifications: (get().notifications || []).filter((n) => n.id !== id) })),
 }))
 
 export default useAppStore
diff --git a/src/types/Post.ts b/src/types/Post.ts
index 3bb06d2..f3210ec 100644
--- a/src/types/Post.ts
+++ b/src/types/Post.ts
@@ -1,13 +1,13 @@
-export interface AttachedPDF {
+export interface AttachedMarkdown {
   name: string
-  url: string
+  content: string
 }
 
 export interface Post {
   id: string
   authorId: string
   content: string
-  attachedPDF?: AttachedPDF
+  attachedMarkdown?: AttachedMarkdown
   endorsements: number
   createdAt: number
 }
diff --git a/src/utils/fileHelpers.ts b/src/utils/fileHelpers.ts
index dd556c4..893ff05 100644
--- a/src/utils/fileHelpers.ts
+++ b/src/utils/fileHelpers.ts
@@ -9,3 +9,24 @@ export const formatTime = (ts: number) => {
   const day = Math.floor(hr / 24)
   return `${day}d`
 }
+
+export const generateToken = (length = 6) => {
+  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
+  let out = ''
+  for (let i = 0; i < length; i++) {
+    out += chars[Math.floor(Math.random() * chars.length)]
+  }
+  return out
+}
+
+export const generateRandomMarkdown = () => {
+  const titles = ['On the Scalability of Models', 'A Study of Cognitive Load', 'Climate Data Methods', 'Quantum Signaling']
+  const title = titles[Math.floor(Math.random() * titles.length)]
+  const intro = 'This is a randomly generated abstract for demo purposes.'
+  const methods = '- Data collection\n- Analysis\n- Validation'
+  const results = 'Preliminary results indicate promising directions.'
+  const conclusion = 'Conclusion: more work is required.'
+  const content = `# ${title}\n\n${intro}\n\n## Methods\n${methods}\n\n## Results\n${results}\n\n## Conclusion\n${conclusion}`
+  const name = `${title.toLowerCase().replace(/[^a-z0-9]+/g,'-').replace(/(^-|-$)/g,'')}.md`
+  return { name, content }
+}