diff --git a/database.js b/database.js
index 79a5c67..c7b0cbe 100644
--- a/database.js
+++ b/database.js
@@ -14,6 +14,17 @@ function initDb() {
       created_at DATETIME DEFAULT CURRENT_TIMESTAMP
     )`);
 
+    // Subject Details Table (Topics, Resources)
+    db.run(`CREATE TABLE IF NOT EXISTS subject_details (
+      id TEXT PRIMARY KEY,
+      subject_id TEXT,
+      type TEXT NOT NULL, -- 'topic', 'link', 'note'
+      content TEXT NOT NULL,
+      is_completed INTEGER DEFAULT 0,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      FOREIGN KEY (subject_id) REFERENCES subjects(id) ON DELETE CASCADE
+    )`);
+
     // Tasks Table
     db.run(`CREATE TABLE IF NOT EXISTS tasks (
       id TEXT PRIMARY KEY,
diff --git a/index.html b/index.html
index da78416..1e0ae05 100644
--- a/index.html
+++ b/index.html
@@ -417,7 +417,7 @@ <h3 style="font-size:12px; font-weight:700; text-transform:uppercase; color:var(
 
 <div id="new-subject-modal" class="modal-backdrop" style="display:none; position:fixed; inset:0; z-index:9998; align-items:center; justify-content:center;">
   <div class="modal-card" style="border-radius:12px; padding:20px; width:320px; box-shadow:0 12px 40px rgba(0,0,0,0.25);">
-    <h3 style="margin:0 0 12px; font-size:18px; font-weight:600;">New subject</h3>
+    <h3 id="subject-modal-title" style="margin:0 0 12px; font-size:18px; font-weight:600;">New subject</h3>
     <label style="display:block; font-size:12px; margin-bottom:4px;">Subject name</label>
     <input id="new-subject-name" type="text" style="width:100%; padding:6px; margin-bottom:12px;" placeholder="e.g. History">
     <label style="display:block; font-size:12px; margin-bottom:6px;">Color</label>
@@ -429,6 +429,32 @@ <h3 style="margin:0 0 12px; font-size:18px; font-weight:600;">New subject</h3>
   </div>
 </div>
 
+<div id="subject-details-modal" class="modal-backdrop" style="display:none; position:fixed; inset:0; z-index:9998; align-items:center; justify-content:center;">
+  <div class="modal-card" style="border-radius:12px; padding:24px; width:480px; max-height: 80vh; overflow-y: auto; box-shadow:0 12px 40px rgba(0,0,0,0.25);">
+    <div style="display:flex; justify-content:space-between; align-items:center; margin-bottom:20px;">
+      <h3 id="detail-modal-subject-name" style="margin:0; font-size:20px; font-weight:700;">Subject Details</h3>
+      <button id="subject-details-close" style="background:none; border:none; font-size:24px; cursor:pointer;">&times;</button>
+    </div>
+    
+    <div style="margin-bottom: 24px;">
+      <h4 style="font-size:12px; font-weight:700; text-transform:uppercase; color:var(--color-text-tertiary); margin-bottom:12px;">Add Topic or Resource</h4>
+      <div style="display:flex; gap:8px;">
+        <select id="detail-type-select" style="padding:6px; border-radius:4px; border:1px solid var(--color-border-secondary);">
+          <option value="topic">Topic</option>
+          <option value="link">Resource Link</option>
+          <option value="note">Note</option>
+        </select>
+        <input id="detail-content-input" type="text" style="flex:1; padding:6px; border-radius:4px; border:1px solid var(--color-border-secondary);" placeholder="Enter topic, link or note...">
+        <button id="add-detail-btn" class="btn btn-primary" style="padding:6px 12px;">Add</button>
+      </div>
+    </div>
+
+    <div id="subject-details-list">
+      <!-- Details will be injected here -->
+    </div>
+  </div>
+</div>
+
 <div id="new-task-modal" class="modal-backdrop" style="display:none; position:fixed; inset:0;  z-index:9998; align-items:center; justify-content:center;">
   <div class="modal-card" style=" border-radius:12px; padding:20px; width:320px; box-shadow:0 12px 40px rgba(0,0,0,0.25);">
     <h3 style="margin:0 0 12px; font-size:18px; font-weight:600;">New task</h3>
diff --git a/js/app.js b/js/app.js
index 9bfd993..72cd751 100644
--- a/js/app.js
+++ b/js/app.js
@@ -77,6 +77,7 @@ const SUBJECT_COLORS = [
 ];
 
 let selectedNewSubjectColor = SUBJECT_COLORS[0];
+let editingSubjectId = null;
 
 function escapeHtml(s) {
   return String(s)
@@ -87,6 +88,7 @@ function escapeHtml(s) {
 }
 
 const newSubjectModal = document.getElementById('new-subject-modal');
+const subjectModalTitle = document.getElementById('subject-modal-title');
 const newSubjectName = document.getElementById('new-subject-name');
 const newSubjectColorsEl = document.getElementById('new-subject-colors');
 const newSubjectCancel = document.getElementById('new-subject-cancel');
@@ -102,15 +104,88 @@ function syncNewSubjectColorSwatches() {
   });
 }
 
-function openNewSubjectModal() {
+function openNewSubjectModal(subject = null) {
   if (!newSubjectModal || !newSubjectName) return;
-  newSubjectName.value = '';
-  selectedNewSubjectColor = SUBJECT_COLORS[0];
+  
+  if (subject) {
+    editingSubjectId = subject.id;
+    subjectModalTitle.textContent = 'Edit Subject';
+    newSubjectName.value = subject.name;
+    selectedNewSubjectColor = subject.color || SUBJECT_COLORS[0];
+  } else {
+    editingSubjectId = null;
+    subjectModalTitle.textContent = 'New Subject';
+    newSubjectName.value = '';
+    selectedNewSubjectColor = SUBJECT_COLORS[0];
+  }
+  
   syncNewSubjectColorSwatches();
   newSubjectModal.style.display = 'flex';
   newSubjectName.focus();
 }
 
+const subjectDetailsModal = document.getElementById('subject-details-modal');
+const detailModalSubjectName = document.getElementById('detail-modal-subject-name');
+const subjectDetailsList = document.getElementById('subject-details-list');
+const detailTypeSelect = document.getElementById('detail-type-select');
+const detailContentInput = document.getElementById('detail-content-input');
+const addDetailBtn = document.getElementById('add-detail-btn');
+const subjectDetailsClose = document.getElementById('subject-details-close');
+let activeDetailSubjectId = null;
+
+async function openSubjectDetails(subjectId) {
+  const subject = store.subjects.find(s => s.id === subjectId);
+  if (!subject) return;
+  
+  activeDetailSubjectId = subjectId;
+  detailModalSubjectName.textContent = subject.name;
+  subjectDetailsModal.style.display = 'flex';
+  renderSubjectDetails();
+}
+
+async function renderSubjectDetails() {
+  if (!activeDetailSubjectId) return;
+  const details = await store.fetchSubjectDetails(activeDetailSubjectId);
+  
+  if (details.length === 0) {
+    subjectDetailsList.innerHTML = '<div style="text-align:center; color:var(--color-text-tertiary); padding:20px;">No topics or resources yet.</div>';
+  } else {
+    subjectDetailsList.innerHTML = details.map(d => {
+      const icon = d.type === 'topic' ? '📚' : (d.type === 'link' ? '🔗' : '📝');
+      const isCompleted = d.is_completed === 1;
+      return `
+        <div class="detail-item" style="display:flex; align-items:center; gap:12px; padding:10px; border-bottom:1px solid var(--color-border-tertiary);">
+          <span style="font-size:16px;">${icon}</span>
+          <div style="flex:1; ${isCompleted ? 'text-decoration:line-through; opacity:0.6;' : ''}">
+            ${d.type === 'link' ? `<a href="${escapeHtml(d.content)}" target="_blank" style="color:var(--color-text-info);">${escapeHtml(d.content)}</a>` : escapeHtml(d.content)}
+          </div>
+          <div style="display:flex; gap:8px;">
+            ${d.type === 'topic' ? `<input type="checkbox" ${isCompleted ? 'checked' : ''} class="toggle-detail-completion" data-id="${d.id}">` : ''}
+            <button class="delete-detail-btn" data-id="${d.id}" style="background:none; border:none; color:var(--color-text-danger); cursor:pointer;">&times;</button>
+          </div>
+        </div>
+      `;
+    }).join('');
+
+    // Attach listeners
+    subjectDetailsList.querySelectorAll('.toggle-detail-completion').forEach(cb => {
+      cb.addEventListener('change', async (e) => {
+        await store.updateSubjectDetail(e.target.dataset.id, { is_completed: e.target.checked ? 1 : 0 });
+        renderSubjectDetails();
+      });
+    });
+
+    subjectDetailsList.querySelectorAll('.delete-detail-btn').forEach(btn => {
+      btn.addEventListener('click', async (e) => {
+        if (confirm('Delete this item?')) {
+          await store.deleteSubjectDetail(e.target.dataset.id);
+          renderSubjectDetails();
+        }
+      });
+    });
+  }
+}
+
 function renderSidebarSubjects() {
   const listEl = document.getElementById('subjects-sidebar-list');
   if (!listEl) return;
@@ -131,9 +206,43 @@ function renderSidebarSubjects() {
     const n = countBySubject[s.id] ?? 0;
     const safeColor = s.color ? escapeHtml(s.color) : 'var(--color-text-info)';
     return `<div class="nav-item subject-sidebar-item" data-subject-id="${escapeHtml(s.id)}">
-      <span class="nav-dot" style="background:${safeColor}"></span>${escapeHtml(s.name)}<span class="badge">${n}</span>
+      <span class="nav-dot" style="background:${safeColor}"></span>
+      <span class="subject-name" style="flex:1;">${escapeHtml(s.name)}</span>
+      <span class="badge">${n}</span>
+      <div class="subject-actions" style="display:none; margin-left:8px; gap:4px;">
+        <button class="edit-subject-btn" title="Edit" style="background:none; border:none; font-size:12px; cursor:pointer;">✏️</button>
+        <button class="delete-subject-btn" title="Delete" style="background:none; border:none; font-size:12px; cursor:pointer;">🗑️</button>
+      </div>
     </div>`;
   }).join('');
+
+  // Attach sidebar listeners
+  listEl.querySelectorAll('.subject-sidebar-item').forEach(el => {
+    const subjectId = el.dataset.subjectId;
+    
+    el.addEventListener('mouseenter', () => {
+      el.querySelector('.subject-actions').style.display = 'flex';
+    });
+    el.addEventListener('mouseleave', () => {
+      el.querySelector('.subject-actions').style.display = 'none';
+    });
+
+    el.addEventListener('click', (e) => {
+      if (e.target.closest('.subject-actions')) return;
+      openSubjectDetails(subjectId);
+    });
+
+    el.querySelector('.edit-subject-btn').addEventListener('click', (e) => {
+      e.stopPropagation();
+      const subject = store.subjects.find(s => s.id === subjectId);
+      openNewSubjectModal(subject);
+    });
+
+    el.querySelector('.delete-subject-btn').addEventListener('click', (e) => {
+      e.stopPropagation();
+      store.deleteSubject(subjectId);
+    });
+  });
 }
 
 const newTaskModal = document.getElementById('new-task-modal');
@@ -897,11 +1006,38 @@ document.addEventListener('DOMContentLoaded', () => {
 
   if (newSubjectSave) {
     newSubjectSave.addEventListener('click', async () => {
-      const ok = await store.addSubject({ name: newSubjectName.value, color: selectedNewSubjectColor });
+      const payload = { name: newSubjectName.value, color: selectedNewSubjectColor };
+      let ok = false;
+      if (editingSubjectId) {
+        ok = await store.updateSubject(editingSubjectId, payload);
+      } else {
+        ok = await store.addSubject(payload);
+      }
       if (ok && newSubjectModal) newSubjectModal.style.display = 'none';
     });
   }
 
+  if (subjectDetailsClose) {
+    subjectDetailsClose.addEventListener('click', () => {
+      subjectDetailsModal.style.display = 'none';
+      activeDetailSubjectId = null;
+    });
+  }
+
+  if (addDetailBtn) {
+    addDetailBtn.addEventListener('click', async () => {
+      const type = detailTypeSelect.value;
+      const content = detailContentInput.value.trim();
+      if (!content) return;
+      
+      const ok = await store.addSubjectDetail(activeDetailSubjectId, { type, content });
+      if (ok) {
+        detailContentInput.value = '';
+        renderSubjectDetails();
+      }
+    });
+  }
+
   if (newSubjectName) {
     newSubjectName.addEventListener('keydown', (e) => {
       if (e.key === 'Enter') {
diff --git a/js/store.js b/js/store.js
index 5d83807..b4b601c 100644
--- a/js/store.js
+++ b/js/store.js
@@ -36,10 +36,18 @@ export const store = {
 
   async addSubject({ name, color }) {
     const trimmed = String(name || '').trim();
-    if (!trimmed) {
-      alert('Please enter a subject name');
+    if (!trimmed || trimmed.length < 2) {
+      alert('Subject name must be at least 2 characters');
       return false;
     }
+
+    // Check for local duplicates before network request
+    const exists = this.subjects.some(s => s.name.toLowerCase() === trimmed.toLowerCase());
+    if (exists) {
+      alert('Subject already exists');
+      return false;
+    }
+
     try {
       const res = await fetch('/api/subjects', {
         method: 'POST',
@@ -62,6 +70,91 @@ export const store = {
     }
   },
 
+  async updateSubject(id, { name, color }) {
+    try {
+      const res = await fetch(`/api/subjects/${id}`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ name, color })
+      });
+      if (!res.ok) throw new Error('Update failed');
+      const subsRes = await fetch('/api/subjects');
+      this.subjects = await subsRes.json();
+      this.notify();
+      return true;
+    } catch (e) {
+      console.error('Failed to update subject', e);
+      return false;
+    }
+  },
+
+  async deleteSubject(id) {
+    if (!confirm('Are you sure? This will delete all tasks and resources for this subject.')) return;
+    try {
+      const res = await fetch(`/api/subjects/${id}`, { method: 'DELETE' });
+      if (!res.ok) throw new Error('Delete failed');
+      
+      const [subsRes, tasksRes] = await Promise.all([
+        fetch('/api/subjects'),
+        fetch('/api/tasks')
+      ]);
+      this.subjects = await subsRes.json();
+      this.tasks = await tasksRes.json();
+      this.notify();
+    } catch (e) {
+      console.error('Failed to delete subject', e);
+    }
+  },
+
+  async fetchSubjectDetails(id) {
+    try {
+      const res = await fetch(`/api/subjects/${id}/details`);
+      return await res.json();
+    } catch (e) {
+      console.error('Failed to fetch subject details', e);
+      return [];
+    }
+  },
+
+  async addSubjectDetail(subjectId, { type, content }) {
+    try {
+      const res = await fetch(`/api/subjects/${subjectId}/details`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ type, content })
+      });
+      if (!res.ok) throw new Error('Add detail failed');
+      return await res.json();
+    } catch (e) {
+      console.error('Failed to add subject detail', e);
+      return null;
+    }
+  },
+
+  async updateSubjectDetail(detailId, fields) {
+    try {
+      const res = await fetch(`/api/subjects/details/${detailId}`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(fields)
+      });
+      return res.ok;
+    } catch (e) {
+      console.error('Failed to update detail', e);
+      return false;
+    }
+  },
+
+  async deleteSubjectDetail(detailId) {
+    try {
+      const res = await fetch(`/api/subjects/details/${detailId}`, { method: 'DELETE' });
+      return res.ok;
+    } catch (e) {
+      console.error('Failed to delete detail', e);
+      return false;
+    }
+  },
+
   // ================= UPDATED FUNCTION =================
   async addTasks(newTasks) {
     try {
diff --git a/server.js b/server.js
index 877f766..0c3e758 100644
--- a/server.js
+++ b/server.js
@@ -240,6 +240,13 @@ app.get('/api/subjects', (req, res) => {
   });
 });
 
+app.get('/api/subjects/:id/details', (req, res) => {
+  db.all('SELECT * FROM subject_details WHERE subject_id = ?', [req.params.id], (err, rows) => {
+    if (err) return res.status(500).json({ error: err.message });
+    res.json(rows);
+  });
+});
+
 const ALLOWED_SUBJECT_COLORS = new Set([
   'var(--color-text-info)',
   'var(--color-text-success)',
@@ -252,24 +259,102 @@ const ALLOWED_SUBJECT_COLORS = new Set([
 app.post('/api/subjects', (req, res) => {
   const name = String(req.body?.name || '').trim();
   let color = String(req.body?.color || '').trim() || 'var(--color-text-info)';
-  if (!name) {
-    return res.status(400).json({ error: 'Subject name is required' });
+  
+  if (!name || name.length < 2) {
+    return res.status(400).json({ error: 'Subject name must be at least 2 characters' });
   }
-  if (!ALLOWED_SUBJECT_COLORS.has(color)) {
-    color = 'var(--color-text-info)';
+
+  // Check for duplicates
+  db.get('SELECT id FROM subjects WHERE LOWER(name) = LOWER(?)', [name], (err, row) => {
+    if (err) return res.status(500).json({ error: err.message });
+    if (row) return res.status(400).json({ error: 'Subject already exists' });
+
+    if (!ALLOWED_SUBJECT_COLORS.has(color)) {
+      color = 'var(--color-text-info)';
+    }
+    const shortCode = name.replace(/[^a-zA-Z0-9]/g, '').toUpperCase().slice(0, 4) || 'SUB';
+    const id = `sub_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`;
+    db.run(
+      'INSERT INTO subjects (id, name, short_code, color) VALUES (?, ?, ?, ?)',
+      [id, name, shortCode, color],
+      function (err) {
+        if (err) return res.status(500).json({ error: err.message });
+        res.status(201).json({ id, name, short_code: shortCode, color });
+      }
+    );
+  });
+});
+
+app.put('/api/subjects/:id', (req, res) => {
+  const { name, color } = req.body;
+  if (!name || name.length < 2) {
+    return res.status(400).json({ error: 'Subject name must be at least 2 characters' });
   }
+
   const shortCode = name.replace(/[^a-zA-Z0-9]/g, '').toUpperCase().slice(0, 4) || 'SUB';
-  const id = `sub_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`;
+  
+  db.run(
+    'UPDATE subjects SET name = ?, color = ?, short_code = ? WHERE id = ?',
+    [name, color, shortCode, req.params.id],
+    function (err) {
+      if (err) return res.status(500).json({ error: err.message });
+      res.json({ success: true, changes: this.changes });
+    }
+  );
+});
+
+app.delete('/api/subjects/:id', (req, res) => {
+  db.run('DELETE FROM subjects WHERE id = ?', [req.params.id], function (err) {
+    if (err) return res.status(500).json({ error: err.message });
+    // Also delete tasks associated with this subject
+    db.run('DELETE FROM tasks WHERE subject_id = ?', [req.params.id]);
+    // Also delete details
+    db.run('DELETE FROM subject_details WHERE subject_id = ?', [req.params.id]);
+    res.json({ success: true, changes: this.changes });
+  });
+});
+
+app.post('/api/subjects/:id/details', (req, res) => {
+  const { type, content } = req.body;
+  if (!type || !content) return res.status(400).json({ error: 'Type and content are required' });
+
+  const id = `det_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`;
   db.run(
-    'INSERT INTO subjects (id, name, short_code, color) VALUES (?, ?, ?, ?)',
-    [id, name, shortCode, color],
+    'INSERT INTO subject_details (id, subject_id, type, content) VALUES (?, ?, ?, ?)',
+    [id, req.params.id, type, content],
     function (err) {
       if (err) return res.status(500).json({ error: err.message });
-      res.status(201).json({ id, name, short_code: shortCode, color });
+      res.status(201).json({ id, type, content });
     }
   );
 });
 
+app.delete('/api/subjects/details/:detailId', (req, res) => {
+  db.run('DELETE FROM subject_details WHERE id = ?', [req.params.detailId], function (err) {
+    if (err) return res.status(500).json({ error: err.message });
+    res.json({ success: true });
+  });
+});
+
+app.put('/api/subjects/details/:detailId', (req, res) => {
+  const { is_completed, content } = req.body;
+  let query = 'UPDATE subject_details SET ';
+  const params = [];
+  const updates = [];
+  if (is_completed !== undefined) { updates.push('is_completed = ?'); params.push(is_completed); }
+  if (content !== undefined) { updates.push('content = ?'); params.push(content); }
+  
+  if (updates.length === 0) return res.status(400).json({ error: 'No fields to update' });
+  
+  query += updates.join(', ') + ' WHERE id = ?';
+  params.push(req.params.detailId);
+  
+  db.run(query, params, function (err) {
+    if (err) return res.status(500).json({ error: err.message });
+    res.json({ success: true });
+  });
+});
+
 // ================= TASKS =================
 app.get('/api/tasks', (req, res) => {
   db.all('SELECT * FROM tasks ORDER BY due_at ASC', (err, rows) => {