:root {
  /* Backgrounds */
  --bg:             #ffffff;
  --surface:        #ffffff;
  --surface-2:      #f6f7f9;
  --surface-3:      #eff1f4;

  /* Borders */
  --border:         #e2e5ea;
  --border-light:   #eef0f3;

  /* Text */
  --text:           #1a1d23;
  --text-secondary: #4b5563;
  --text-muted:     #9ca3af;

  /* Accent — Python blue */
  --accent:         #0066cc;
  --accent-hover:   #0055aa;
  --accent-bg:      #eef4ff;
  --accent-border:  #bfd5f5;

  /* Difficulty */
  --easy:           #1a7f37;
  --easy-bg:        #dafbe1;
  --easy-border:    #aceebb;
  --medium:         #9a6700;
  --medium-bg:      #fff8c5;
  --medium-border:  #f5c211;
  --hard:           #cf222e;
  --hard-bg:        #ffebe9;
  --hard-border:    #ffcecb;

  /* Status */
  --success:        #1a7f37;
  --success-bg:     #dafbe1;
  --error:          #cf222e;
  --error-bg:       #ffebe9;

  /* Code */
  --code-bg:        #f6f8fa;
  --code-border:    #e2e5ea;

  /* Terminal */
  --terminal-bg:    #0d1117;
  --terminal-text:  #e6edf3;
  --terminal-green: #3fb950;

  /* Typography */
  --font-ui:   'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', Consolas, monospace;

  /* Sizing */
  --radius:       6px;
  --radius-sm:    4px;
  --radius-xs:    3px;
  --shadow-sm:    0 1px 3px rgba(0,0,0,0.06);
  --shadow-md:    0 2px 8px rgba(0,0,0,0.08);
  --transition:   0.15s ease;
  --sidebar-width: 260px;
  --content-max:   740px;
}

[data-theme="dark"] {
  --bg:             #0d1117;
  --surface:        #161b22;
  --surface-2:      #1c2128;
  --surface-3:      #222830;

  --border:         #30363d;
  --border-light:   #21262d;

  --text:           #e6edf3;
  --text-secondary: #8b949e;
  --text-muted:     #6e7681;

  --accent:         #58a6ff;
  --accent-hover:   #79b8ff;
  --accent-bg:      #0d2545;
  --accent-border:  #1f4070;

  --easy:           #3fb950;
  --easy-bg:        #0d2e1a;
  --easy-border:    #1a5c30;
  --medium:         #d29922;
  --medium-bg:      #2d1f00;
  --medium-border:  #5a3e00;
  --hard:           #f85149;
  --hard-bg:        #2d0f0e;
  --hard-border:    #5c1e1c;

  --success:        #3fb950;
  --success-bg:     #0d2e1a;
  --error:          #f85149;
  --error-bg:       #2d0f0e;

  --code-bg:        #0d1117;
  --code-border:    #30363d;
}