fix: force primary button text white via late CSS override

app.py

@@ -412,9 +412,21 @@ fieldset label.selected input[type="radio"] {
 }
 """
 
+extra_css = """
+<style>
+.gradio-container button.gr-button-primary,
+.gradio-container button.gr-button-primary span,
+.gradio-container button.gr-button-primary p {
+    color: #ffffff !important;
+    -webkit-text-fill-color: #ffffff !important;
+}
+</style>
+"""
+
 with gr.Blocks(title="UltraData-Math L3 Generator", css=custom_css, theme=gr.themes.Soft()) as demo:
     gr.HTML('<h1 class="main-title">🧮 UltraData-Math L3 Generator</h1>')
     gr.HTML('<p class="subtitle">✨ Next-Gen Mathematical Data Synthesis Powered by LLM ✨</p>')
+    gr.HTML(extra_css)
     
     with gr.Tabs():
         # Q&A Synthesis Tab