diff --git a/src/components/Header.astro b/src/components/Header.astro
index e2bb6db..473e7e1 100644
--- a/src/components/Header.astro
+++ b/src/components/Header.astro
@@ -1,10 +1,13 @@
 ---
-// No props needed for this simple header
+// src/components/Header.astro
+import ThemeToggler from './ThemeToggler.astro';
 ---
 <header>
   <h1>DSAS CCA Viewer</h1>
+
   <nav>
     <a href="/">Clubs</a>
     <a href="/staff">Staff</a>
+    <ThemeToggler/>
   </nav>
 </header>
\ No newline at end of file
diff --git a/src/components/ThemeToggler.astro b/src/components/ThemeToggler.astro
new file mode 100644
index 0000000..e4bbc05
--- /dev/null
+++ b/src/components/ThemeToggler.astro
@@ -0,0 +1,108 @@
+---
+// src/components/ThemeToggler.astro
+---
+<style>
+:root {
+  --toggle-bg:        #e2e8f0;
+  --toggle-bg-dark:   #334155;
+  --knob-bg:          #ffffff;
+  --icon-color:       #facc15;   /* sun / moon colour */
+}
+.theme-toggle-button{
+  position:relative;
+  width:3rem;
+  height:1.5rem;
+  border-radius:9999px;
+  background:var(--toggle-bg,#e2e8f0);
+  border:none;
+  cursor:pointer;
+  padding:0;
+  display:flex;
+  align-items:center;
+  transition:background .3s ease;
+}
+.theme-toggle-button .knob{
+  position:absolute;
+  top:0.125rem;
+  left:0.125rem;
+  width:1.25rem;
+  height:1.25rem;
+  border-radius:9999px;
+  background:var(--knob-bg,#fff);
+  display:flex;
+  align-items:center;
+  justify-content:center;
+  transition:transform .3s ease, background .3s ease;
+  box-shadow:0 1px 3px rgba(0,0,0,0.2);
+}
+body.dark-mode .theme-toggle-button{
+  background:var(--toggle-bg-dark,#334155);
+}
+body.dark-mode .theme-toggle-button .knob{
+  transform:translateX(1.5rem);
+}
+.theme-toggle-button svg{
+  width:0.75rem;
+  height:0.75rem;
+  color:var(--icon-color,#facc15);
+}
+body.dark-mode .theme-toggle-button svg.sun{display:none;}
+body:not(.dark-mode) .theme-toggle-button svg.moon{display:none;}
+</style>
+
+<button id="themeToggleBtn" class="theme-toggle-button" aria-label="Toggle theme" aria-pressed="false">
+  <div class="knob">
+    <!-- Sun icon -->
+    <svg class="sun" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="currentColor">
+      <path d="M12 18a6 6 0 110-12 6 6 0 010 12z"/>
+      <path d="M12 2v2M12 20v2M4.22 4.22l1.42 1.42M18.36 18.36l1.42 1.42M2 12h2M20 12h2M4.22 19.78l1.42-1.42M18.36 5.64l1.42-1.42"/>
+    </svg>
+    <!-- Moon icon -->
+    <svg class="moon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="currentColor">
+      <path d="M21 12.79A9 9 0 1111.21 3 7 7 0 0021 12.79z"/>
+    </svg>
+  </div>
+</button>
+
+<script>
+  const themeToggleBtn = document.getElementById('themeToggleBtn');
+  const body = document.body;
+  const preferDarkQuery = '(prefers-color-scheme: dark)';
+
+  function applyTheme(theme){
+    if(theme==='dark'){
+      body.classList.add('dark-mode');
+      themeToggleBtn?.setAttribute('aria-pressed','true');
+    }else{
+      body.classList.remove('dark-mode');
+      themeToggleBtn?.setAttribute('aria-pressed','false');
+    }
+  }
+
+  function toggleTheme(){
+    const isDarkMode = body.classList.contains('dark-mode');
+    const newTheme = isDarkMode ? 'light' : 'dark';
+    localStorage.setItem('theme', newTheme);
+    applyTheme(newTheme);
+  }
+
+  function loadTheme(){
+    const savedTheme = localStorage.getItem('theme');
+    const systemPrefersDark = window.matchMedia(preferDarkQuery).matches;
+    if(savedTheme){
+      applyTheme(savedTheme);
+    }else if(systemPrefersDark){
+      applyTheme('dark');
+    }else{
+      applyTheme('light');
+    }
+  }
+
+  loadTheme();
+  themeToggleBtn?.addEventListener('click', toggleTheme);
+  window.matchMedia(preferDarkQuery).addEventListener('change', (e)=>{
+    if(!localStorage.getItem('theme')){
+      applyTheme(e.matches ? 'dark' : 'light');
+    }
+  });
+</script>
\ No newline at end of file
diff --git a/src/styles/global.css b/src/styles/global.css
index 983867f..ec3a662 100644
--- a/src/styles/global.css
+++ b/src/styles/global.css
@@ -1,20 +1,84 @@
+/* src/styles/global.css */
+
 /* Basic Reset & Defaults */
+:root {
+  /* Light Mode Variables (Default) */
+  --bg-color: #f4f7f6;
+  --text-color: #333;
+  --header-bg: #2c3e50;
+  --header-text: white;
+  --header-link-hover: #1abc9c;
+  --footer-bg: #34495e;
+  --footer-text: #ecf0f1;
+  --card-bg: white;
+  --card-box-shadow: rgba(0,0,0,0.1);
+  --card-box-shadow-hover: rgba(0,0,0,0.15);
+  --card-border: #eee; /* For borders like in card-details-section */
+  --search-bar-bg: #ffffff;
+  --search-bar-border: #ddd;
+  --search-bar-text: #333; /* Text inside input fields */
+  --button-bg: #1abc9c;
+  --button-text: white;
+  --button-bg-hover: #16a085;
+  --placeholder-text: #888;
+  --modal-content-bg: white;
+  --modal-overlay-bg: rgba(0, 0, 0, 0.6);
+  --modal-header-border: #eee;
+  --modal-close-button-color: #888;
+  --modal-close-button-hover-color: #333;
+  --accent-color: #1abc9c; /* For things like modal h3 */
+  --strong-text-color: #555;
+  --link-color: #1abc9c; /* General link color if needed */
+}
+
+body.dark-mode {
+  /* Dark Mode Variable Overrides */
+  --bg-color: #1a1a1a; /* Darker background */
+  --text-color: #e0e0e0; /* Lighter text */
+  --header-bg: #1f2937; /* Slightly different dark header */
+  --header-text: #e0e0e0;
+  --header-link-hover: #58c1ac; /* Lighter accent for hover */
+  --footer-bg: #111827; /* Darker footer */
+  --footer-text: #c7c7c7;
+  --card-bg: #2d2d2d; /* Dark card background */
+  --card-box-shadow: rgba(255,255,255,0.05); /* Lighter shadow for dark mode */
+  --card-box-shadow-hover: rgba(255,255,255,0.1);
+  --card-border: #444; /* Darker border */
+  --search-bar-bg: #2d2d2d;
+  --search-bar-border: #555;
+  --search-bar-text: #e0e0e0; /* Text inside input fields */
+  --button-bg: #58c1ac; /* Lighter accent for buttons */
+  --button-text: #1a1a1a; /* Darker text on light buttons */
+  --button-bg-hover: #4aa08c;
+  --placeholder-text: #777;
+  --modal-content-bg: #2d2d2d;
+  --modal-overlay-bg: rgba(0, 0, 0, 0.8); /* Darker overlay */
+  --modal-header-border: #444;
+  --modal-close-button-color: #aaa;
+  --modal-close-button-hover-color: #e0e0e0;
+  --accent-color: #58c1ac;
+  --strong-text-color: #bbb;
+  --link-color: #58c1ac;
+}
+
+
 body {
   font-family: sans-serif;
   margin: 0;
-  background-color: #f4f7f6;
-  color: #333;
+  background-color: var(--bg-color); /* USE VAR */
+  color: var(--text-color);          /* USE VAR */
   line-height: 1.6;
-  box-sizing: border-box; /* Add to body and inherit */
+  box-sizing: border-box;
+  transition: background-color 0.3s ease, color 0.3s ease; /* Smooth transition */
 }
 
 *, *::before, *::after {
-  box-sizing: inherit; /* Ensure all elements use the same box model */
+  box-sizing: inherit;
 }
 
 header {
-  background-color: #2c3e50;
-  color: white;
+  background-color: var(--header-bg); /* USE VAR */
+  color: var(--header-text);       /* USE VAR */
   padding: 1rem 2rem;
   display: flex;
   justify-content: space-between;
@@ -23,19 +87,40 @@ header {
 
 header h1 {
   margin: 0;
-  font-size: 1.8rem;
+  font-size: 1.66rem;
+}
+
+header nav{
+  display:flex;          /* put the links and the toggle in one row   */
+  align-items:center;    /* vertically centre them                    */
+  gap:1.5rem;            /* space between the links and the toggle    */
 }
 
 header nav a {
-  color: white;
+  color: var(--header-text); /* USE VAR */
   text-decoration: none;
-  margin-left: 1.5rem;
-  font-size: 1.1rem;
+  margin-left: 0;
+  font-size: 1.33rem;
   transition: color 0.2s ease-in-out;
 }
 
 header nav a:hover {
-  color: #1abc9c;
+  color: var(--header-link-hover); /* USE VAR */
+}
+
+/* Theme Toggle Button Style */
+.theme-toggle-button {
+    background: none;
+    border: 1px solid var(--header-text);
+    color: var(--header-text);
+    padding: 0.4rem 0.8rem;
+    border-radius: 4px;
+    cursor: pointer;
+    font-size: 1rem;
+    margin-left: 0;
+}
+body.dark-mode .theme-toggle-button {
+    border-color: var(--header-text); /* Or a specific dark mode border color */
 }
 
 main {
@@ -47,46 +132,57 @@ main {
 footer {
   text-align: center;
   padding: 1.5rem;
-  background-color: #34495e;
-  color: #ecf0f1;
+  background-color: var(--footer-bg); /* USE VAR */
+  color: var(--footer-text);       /* USE VAR */
   margin-top: 2rem;
 }
 
 /* Search Bar Styles - Desktop First */
 .search-bar-container {
-  background-color: #ffffff;
+  background-color: var(--search-bar-bg); /* USE VAR */
   padding: 1.5rem;
   border-radius: 8px;
-  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
+  box-shadow: 0 2px 10px var(--card-box-shadow); /* USE VAR for consistency with cards */
   margin-bottom: 2rem;
   display: flex;
   flex-wrap: wrap;
   gap: 1rem;
-  align-items: center; /* Aligns items vertically if they have different heights on one line */
+  align-items: center;
 }
 
 .search-bar-container input[type="text"],
 .search-bar-container input[type="number"],
 .search-bar-container select {
+  background-color: var(--bg-color); /* Match page bg or use specific input bg */
+  color: var(--search-bar-text);     /* USE VAR */
   padding: 0.75rem;
-  border: 1px solid #ddd;
+  border: 1px solid var(--search-bar-border); /* USE VAR */
   border-radius: 4px;
   font-size: 1rem;
-  line-height: 1.4; /* Ensure consistent line height */
+  line-height: 1.4;
   flex-grow: 1;
   flex-shrink: 1;
-  /* min-width helps with wrapping on desktop */
+}
+/* Handle select dropdown arrow color for dark mode (can be tricky cross-browser) */
+/* For modern browsers, accent-color can influence form controls */
+.search-bar-container select {
+    accent-color: var(--accent-color);
+}
+/* Placeholder color for inputs */
+.search-bar-container input::placeholder {
+    color: var(--placeholder-text);
+    opacity: 0.7;
 }
 
 .search-bar-container input[type="text"] {
-  flex-basis: 300px; /* Ideal width on desktop */
-  min-width: 250px; /* Minimum it should shrink to on desktop before wrapping */
+  flex-basis: 300px;
+  min-width: 250px;
 }
 
 .search-bar-container select,
 .search-bar-container input[type="number"] {
-  flex-basis: 200px; /* Ideal width for these filters on desktop */
-  min-width: 150px; /* Minimum they should shrink to */
+  flex-basis: 200px;
+  min-width: 150px;
 }
 
 
@@ -98,34 +194,41 @@ footer {
   }
   header nav {
     margin-top: 0.5rem;
+    width: 100%; /* Ensure nav takes full width for button alignment */
+    display: flex;
+    justify-content: space-between; /* Align nav items and toggle button */
+    align-items: center;
+  }
+  header nav div { /* Assuming nav links are wrapped in a div */
+    display: flex;
   }
   header nav a {
     margin-left: 0;
     margin-right: 1rem;
   }
+  .theme-toggle-button {
+    margin-left: auto; /* Push toggle to the right */
+  }
 
-  /* === Search Bar Mobile Styles === */
+  
   .search-bar-container {
-    flex-direction: column; /* Stack items vertically */
-    align-items: stretch;   /* Make items take up full available width */
-    padding: 1rem;          /* Adjust padding for mobile */
-    gap: 0.75rem;           /* Adjust gap between stacked items */
+    flex-direction: column;
+    align-items: stretch;
+    padding: 1rem;
+    gap: 0.75rem;
   }
 
   .search-bar-container input[type="text"],
   .search-bar-container input[type="number"],
   .search-bar-container select {
-    width: 100%;            /* Make each item take full width */
-    font-size: 0.9rem;      /* Slightly smaller font for better fit */
-    padding: 0.65rem 0.75rem; /* Adjust padding (vertical, horizontal) */
-    /* Remove flex-basis, min-width for mobile as width: 100% takes precedence */
+    width: 100%;
+    font-size: 0.9rem;
+    padding: 0.65rem 0.75rem;
     flex-basis: auto;
     min-width: 0;
-    flex-grow: 0; /* Not needed when width is 100% in a column */
-    flex-shrink: 0; /* Not needed when width is 100% in a column */
+    flex-grow: 0;
+    flex-shrink: 0;
   }
-  /* No specific overrides needed for input[type="text"] or input[type="number"] here
-     as they will follow the general rule above for mobile. */
 }
 
 
@@ -138,27 +241,32 @@ footer {
 
 /* Card Styles */
 .card {
-  background-color: white;
+  background-color: var(--card-bg); /* USE VAR */
+  color: var(--text-color); /* Inherit text color from body or set specific */
   border-radius: 8px;
-  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
+  box-shadow: 0 4px 6px var(--card-box-shadow); /* USE VAR */
   overflow: hidden;
-  transition: transform 0.2s ease-in-out, box-shadow 0.2s ease-in-out;
+  transition: transform 0.2s ease-in-out, box-shadow 0.2s ease-in-out, background-color 0.3s ease, color 0.3s ease;
   display: flex;
   flex-direction: column;
 }
 
 .card:hover {
   transform: translateY(-5px);
-  box-shadow: 0 8px 12px rgba(0,0,0,0.15);
+  box-shadow: 0 8px 12px var(--card-box-shadow-hover); /* USE VAR */
 }
 
 .card-photo-container {
   width: 100%;
   aspect-ratio: 16 / 9;
-  background-color: #e0e0e0;
+  background-color: var(--placeholder-text); /* Or a darker placeholder for dark mode */
   overflow: hidden;
   display: block;
 }
+body.dark-mode .card-photo-container {
+    background-color: #4a4a4a; /* Darker placeholder */
+}
+
 
 .card-photo {
   display: block;
@@ -178,7 +286,7 @@ footer {
   margin-top: 0;
   margin-bottom: 0.33rem;
   font-size: 1.33rem;
-  color: #333;
+  color: var(--text-color); /* USE VAR */
 }
 
 .card-content p {
@@ -188,19 +296,24 @@ footer {
   margin-right: 0;
   font-size: 1rem;
   line-height: 1.5;
+  color: var(--text-color); /* USE VAR */
 }
+.card-content p strong {
+    color: var(--strong-text-color); /* USE VAR for strong tags inside paragraphs */
+}
+
 
 .card-info-placeholder {
   font-style: italic;
-  color: #888;
+  color: var(--placeholder-text); /* USE VAR */
   font-size: 0.9rem;
   min-height: 1.2em;
 }
 
-.card-details-section {
+.card-details-section { /* This class is not currently used in ClubCard.tsx for the modal */
   margin-top: 0.75rem;
   padding-top: 0.75rem;
-  border-top: 1px solid #eee;
+  border-top: 1px solid var(--card-border); /* USE VAR */
 }
 
 .card-details-section p {
@@ -209,12 +322,12 @@ footer {
 }
 
 .card-details-section strong {
-  color: #555;
+  color: var(--strong-text-color); /* USE VAR */
 }
 
 .card-button {
-  background-color: #1abc9c;
-  color: white;
+  background-color: var(--button-bg); /* USE VAR */
+  color: var(--button-text);       /* USE VAR */
   border: none;
   padding: 0.6rem 1rem;
   border-radius: 4px;
@@ -226,7 +339,7 @@ footer {
 }
 
 .card-button:hover {
-  background-color: #16a085;
+  background-color: var(--button-bg-hover); /* USE VAR */
 }
 
 /* Loading and Error Messages */
@@ -234,24 +347,33 @@ footer {
   text-align: center;
   font-size: 1.2rem;
   padding: 2rem;
-  color: #555;
+  color: var(--strong-text-color); /* USE VAR */
 }
 
 .error-message {
-  color: #e74c3c;
+  color: #e74c3c; /* Keep specific error color, or make it a variable too */
+}
+body.dark-mode .error-message {
+    color: #ff6b6b; /* Lighter red for dark mode */
 }
 
+
 /* Staff Card Specifics */
-.staff-card {
+.staff-card { /* Staff card inherits .card styles, so it gets dark mode too */
   padding: 1.5rem;
 }
 .staff-card h3 {
   font-size: 1.2rem;
+  color: var(--text-color); /* USE VAR */
 }
 .staff-card p {
   font-size: 1rem;
-  color: #555;
+  color: var(--text-color); /* USE VAR */
 }
+.staff-card p strong {
+    color: var(--strong-text-color);
+}
+
 
 /* Modal Styles */
 .modal-overlay {
@@ -260,7 +382,7 @@ footer {
   left: 0;
   right: 0;
   bottom: 0;
-  background-color: rgba(0, 0, 0, 0.6);
+  background-color: var(--modal-overlay-bg); /* USE VAR */
   display: flex;
   align-items: center;
   justify-content: center;
@@ -269,10 +391,11 @@ footer {
 }
 
 .modal-content {
-  background-color: white;
+  background-color: var(--modal-content-bg); /* USE VAR */
+  color: var(--text-color);                /* USE VAR */
   padding: 2rem;
   border-radius: 8px;
-  box-shadow: 0 5px 15px rgba(0,0,0,0.3);
+  box-shadow: 0 5px 15px var(--card-box-shadow); /* USE VAR */
   width: 90%;
   max-width: 700px;
   max-height: 90vh;
@@ -287,18 +410,18 @@ footer {
   padding-right: 1rem;
 }
 
-.modal-content h2 {
+.modal-content h2 { /* Main title in modal */
   margin-top: 0;
   margin-bottom: 1rem;
-  color: #333;
+  color: var(--text-color); /* USE VAR */
   padding-bottom: 1rem;
-  border-bottom: 1px solid #eee;
+  border-bottom: 1px solid var(--modal-header-border); /* USE VAR */
 }
 
-.modal-content h3 {
+.modal-content h3 { /* Subheadings like "Meta Information" in modal */
   margin-top: 1rem;
   margin-bottom: 0.5rem;
-  color: #1abc9c;
+  color: var(--accent-color); /* USE VAR */
 }
 .modal-content p, .modal-content li {
   margin-top: 0.33rem;
@@ -307,6 +430,10 @@ footer {
   margin-right: 0;
   font-size: 1rem;
   line-height: 1.5;
+  color: var(--text-color); /* USE VAR */
+}
+.modal-content p strong {
+    color: var(--strong-text-color);
 }
 .modal-content ul {
   padding-left: 20px;
@@ -328,10 +455,10 @@ footer {
   border: none;
   font-size: 2rem;
   font-weight: bold;
-  color: #888;
+  color: var(--modal-close-button-color); /* USE VAR */
   cursor: pointer;
   line-height: 1;
 }
 .modal-close-button:hover {
-  color: #333;
+  color: var(--modal-close-button-hover-color); /* USE VAR */
 }
\ No newline at end of file