/* Center ALL nav buttons in vertical nav */
.unit-nav-vertical .nav-btn {
    justify-content: center;
    text-align: center;
}
/* Vertical nav for unit pages */
.unit-nav-vertical {
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
    align-items: stretch;
    max-width: 350px;
    margin: 0 auto 2rem auto;
}
/* Theme Variables */
:root {
  --color-bg: #f8fafc;
  --color-text: #222;
  --color-primary: #3949ab;
  --color-primary-dark: #283593;
  --color-accent: #ffe082;
  --color-footer-bg: linear-gradient(90deg, #3949ab 0%, #1976d2 100%);
  --color-footer-text: #fff;
  --color-btn-text: #fff;
  --color-btn-hover: #283593;
  --color-btn-shadow: 0 2px 8px rgba(60, 60, 100, 0.13);
  --color-card-bg: #fff;
  --color-card-shadow: 0 1px 6px rgba(0, 0, 0, 0.06);
  --color-timer-bg: #fffde7;
  --color-timer-text: #f9a825;
  --color-link: #3949ab;
  --color-link-hover: #1a237e;
  --color-scroll-btn-bg: #3949ab;
  --color-scroll-btn-text: #ffe082;
}

[data-theme="dark"] {
  --color-bg: #181a23;
  --color-text: #e3eafc;
  --color-primary: #222a5c;
  --color-primary-dark: #10153a;
  --color-accent: #ffe082;
  --color-footer-bg: linear-gradient(90deg, #222a5c 0%, #10153a 100%);
  --color-footer-text: #fffde7;
  --color-btn-text: #fffde7;
  --color-btn-hover: #10153a;
  --color-btn-shadow: 0 2px 8px rgba(20, 20, 40, 0.23);
  --color-card-bg: #23263a;
  --color-card-shadow: 0 1px 6px rgba(0,0,0,0.18);
  --color-timer-bg: #23263a;
  --color-timer-text: #ffe082;
  --color-link: #ffe082;
  --color-link-hover: #fffde7;
  --color-scroll-btn-bg: #222a5c;
  --color-scroll-btn-text: #ffe082;
}

/* Scroll to Top Button */
#scrollToTopBtn {
    display: none;
    position: fixed;
    bottom: 2.2rem;
    right: 2.2rem;
    z-index: 1200;
    background: var(--color-scroll-btn-bg);
    color: var(--color-scroll-btn-text);
    border: none;
    border-radius: 50%;
    width: 54px;
    height: 54px;
    font-size: 2.2rem;
    box-shadow: 0 2px 8px rgba(60, 60, 100, 0.18);
    cursor: pointer;
    transition: background 0.2s, transform 0.2s, opacity 0.2s;
    opacity: 0.95;
}
        
@media (max-width: 600px) {
    #scrollToTopBtn {
        right: 1.1rem;
        bottom: 1.1rem;
        width: 44px;
        height: 44px;
        font-size: 1.5rem;
    }
}
.logo-link, .logo-link:visited, .logo-link:active, .logo-link:focus, .logo-link .logo-text {
    text-decoration: none !important;
    border-bottom: none !important;
    box-shadow: none !important;
}
/* Nav button color and contrast */
.nav-btn {
    text-decoration: none;
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: flex-start;
    gap: 1.2rem;
}
.nav-btn:visited,
.nav-btn:active,
.nav-btn:focus,
.nav-btn:hover {
    text-decoration: none;
    background: var(--color-primary);
    color: var(--color-btn-text);
    box-shadow: var(--color-btn-shadow);
    position: relative;
    z-index: 1;
}
.unit-topic {
    color: #fff !important;
}
.nav-btn .unit-label {
    min-width: 70px;
    font-weight: bold;
    font-family: 'Segoe UI', Arial, sans-serif;
    color: var(--color-accent);
    letter-spacing: 0.5px;
    text-align: left;
    z-index: 2;
    position: relative;
    margin-right: 0.5rem;
    display: inline-block;
}
.nav-btn .unit-topic {
    color: var(--color-accent);
    font-weight: 500;
    text-align: left;
    position: static;
    margin: 0;
    display: inline-block;
}
.nav-btn::before {
    display: none;
}
.nav-btn > * {
    position: relative;
    z-index: 3;
}
/* Logo styles */
.logo-link {
    position: absolute;
    top: 1.2rem;
    left: 1.5rem;
    text-decoration: none !important;
}
.logo-link:visited {
    text-decoration: none !important;
    z-index: 100;
}

.logo-text {
    font-family: 'Segoe UI', Arial, sans-serif;
    font-weight: 900;
    font-size: 2.1rem;
    color: #3949ab;
    letter-spacing: 2px;
    background: linear-gradient(90deg, #ffe082 0%, #1976d2 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: 1px 2px 8px rgba(60,60,100,0.08);
    transition: opacity 0.2s;
}

.logo-link:hover .logo-text,
.logo-link:focus .logo-text {
    opacity: 0.7;
}

@media (max-width: 600px) {
    .logo-link {
        top: 0.7rem;
        left: 0.7rem;
    }
    .logo-text {
        font-size: 1.3rem;
    }
}
header h1 {
    font-size: 2.7rem;
    letter-spacing: 1px;
    margin-bottom: 0.5rem;
}

header p {
    font-size: 1.35rem;
    color: #283593;
    margin-bottom: 2rem;
}
/* Footer Bar Styles */
.footer-bar {
    background: var(--color-footer-bg);
    color: var(--color-footer-text);
    padding: 0.5rem 1rem;
    font-size: 0.95rem;
    text-align: center;
    border-top-left-radius: 18px;
    border-top-right-radius: 18px;
    box-shadow: 0 -2px 12px rgba(30, 40, 80, 0.10);
    margin-top: 2rem;
}

.footer-resources {
    margin-bottom: 0.3rem;
}

.footer-bar .resource-link {
    color: #fffde7;
    background: rgba(255, 255, 255, 0.10);
    border-radius: 8px;
    padding: 0.2rem 0.7rem;
    margin: 0 0.5rem;
    font-size: 0.95rem;
    font-weight: 600;
    text-decoration: none;
    display: inline-block;
    transition: background 0.2s, color 0.2s;
}

.footer-bar .resource-link:hover,
.footer-bar .resource-link:focus {
    background: #fffde7;
    color: #3949ab;
}

.footer-text {
    font-size: 0.5rem;
    font-family: 'Segoe Script', 'Brush Script MT', cursive, sans-serif;
    font-size: 1.25rem;
    margin-bottom: 0.2rem;
    letter-spacing: 0.5px;
    color: #ffe082;
    /* allow the footer sentence to wrap naturally and stay readable */
    white-space: normal;
    display: inline-block;
    max-width: min(56ch, 90%);
    line-height: 1.2;
    -webkit-hyphens: auto;
    -ms-hyphens: auto;
    hyphens: auto;
}

.footer-bar span {
    display: block;
}

.footer-bar .footer-copyright {
    font-size: 0.85rem;
    color: #c5cae9;
    opacity: 0.8;
    margin-top: 0.5rem;
}

@media (max-width: 600px) {
    .footer-bar {
        padding: 1.2rem 0.5rem 0.8rem 0.5rem;
        border-radius: 12px 12px 0 0;
    }

    .footer-text {
        font-size: 1.05rem;
    }
}

/* Reset and base styles */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Segoe UI', Arial, sans-serif;
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    transition: background 0.3s, color 0.3s;
}

/* Container */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 2rem;
}

h1,
h2,
h3 {
    font-weight: 700;
    color: #1a237e;
}

/* Navigation grid for 9 sections */
.nav-grid {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
    align-items: center; /* center the buttons horizontally */
}

.nav-btn, button.nav-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    /* Make each nav button a long pill; limit by max-width to avoid overflowing */
    width: 100%;
    max-width: 680px; /* long stick on wide screens */
    padding: 0.9rem 1.1rem;
    font-size: 18px;
    border-radius: 999px; /* full pill */
    border: none;
    background: var(--color-primary);
    color: var(--color-btn-text);
    cursor: pointer;
    transition: background 0.2s, transform 0.2s;
    box-shadow: var(--color-btn-shadow);
    outline: none;
    text-decoration: none;
    font-family: 'Segoe UI', Arial, sans-serif;
    font-weight: 600;
    margin: 0;
}

.nav-btn:focus,
.nav-btn:active {
    outline: none;
    box-shadow: none;
    border: none;
    transform: none;
}

.nav-btn {
    text-decoration: none;
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: flex-start;
    gap: 1.2rem;
}
.nav-btn .unit-label {
    min-width: 70px;
    font-weight: bold;
    font-family: 'Segoe UI', Arial, sans-serif;
    color: var(--color-accent);
    letter-spacing: 0.5px;
    text-align: left;
    z-index: 2;
    position: relative;
    margin-right: 0.5rem;
    display: inline-block;
}
.nav-btn .unit-topic {
    color: var(--color-accent);
    font-weight: 500;
    text-align: left;
    position: static;
    margin: 0;
    display: inline-block;
}

.unit-label {
    min-width: 70px;
    font-weight: bold;
    font-family: 'Segoe UI', Arial, sans-serif;
    color: var(--color-accent);
    letter-spacing: 0.5px;
    text-align: left !important;
    z-index: 2;
    position: relative;
}

.unit-topic {
    position: absolute;
    left: 0;
    width: 100%;
    text-align: center;
    color: var(--color-accent);
    font-weight: 500;
    pointer-events: none;
    z-index: 1;
}

.nav-btn:hover{
    background: var(--color-btn-hover);
    transform: translateY(-2px) scale(1.03);
}

.nav-btn:focus {
    transform: none;
}

/* Question Card */
.question-card {
    background: var(--color-card-bg);
    border-radius: 10px;
    box-shadow: var(--color-card-shadow);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.question-title {
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.choices {
    list-style: none;
    margin-bottom: 1rem;
}

.choice {
    margin-bottom: 0.75rem;
}

.choice input[type="radio"] {
    margin-right: 0.5rem;
}

.feedback {
    margin-top: 0.5rem;
    font-weight: 600;
}

.feedback.correct {
    color: #2e7d32;
}

.feedback.incorrect {
    color: #c62828;
}

/* Timer */
.timer {
    background: var(--color-timer-bg);
    color: var(--color-timer-text);
    font-weight: bold;
    padding: 0.5rem 1rem;
    border-radius: 8px;
    display: inline-block;
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

/* Resources */
.resources {
    margin-top: 2rem;
}

.resource-link {
    display: inline-block;
    margin: 0.5rem 1rem 0.5rem 0;
    color: var(--color-link);
    text-decoration: underline;
    font-weight: 500;
}

.resource-link:hover,
.resource-link:focus {
    color: var(--color-link-hover);
}

/* Cheat sheet panel */
.cheat-sheet-panel {
    position: fixed;
    right: 0;
    top: 0;
    width: 320px;
    max-width: 90vw;
    height: 100vh;
    background: #e3eafc;
    box-shadow: -2px 0 12px rgba(30, 40, 80, 0.08);
    padding: 2rem 1rem;
    overflow-y: auto;
    z-index: 1000;
    transform: translateX(100%);
    transition: transform 0.3s;
}

.cheat-sheet-panel.open {
    transform: translateX(0);
}

.cheat-sheet-toggle {
    position: fixed;
    right: 1.5rem;
    bottom: 1.5rem;
    background: #3949ab;
    color: #ffe082;
    border: none;
    border-radius: 50%;
    width: 54px;
    height: 54px;
    font-size: 2rem;
    box-shadow: 0 2px 8px rgba(60, 60, 100, 0.13);
    cursor: pointer;
    z-index: 1100;
}

/* Theme Toggle Switch - Modern, Rounded, Sliding Handle */
#themeToggleBtn {
  position: fixed;
  top: 1.5rem;
  right: 1.5rem;
  z-index: 1200;
      width: 48px;
  height: 24px;
  background: #55585d;
  border: none;
  border-radius: 12px;
  display: flex;
  align-items: center;
  cursor: pointer;
  transition: background 0.5s;
  box-shadow: 0 1px 4px rgba(60, 60, 100, 0.10);
  padding: 0;
}
#themeToggleBtn.on {
  background: #fff;
}
#themeToggleBtn:focus {
  outline: none;
}
#themeToggleBtn .toggle-handle {
  width: 20px;
  height: 20px;
  background: #fff;
  border-radius: 50%;
  box-shadow: 0 1px 4px rgba(60, 60, 100, 0.13);
  transition: transform 0.5s cubic-bezier(.4,2,.6,1), background 0.5s;
  transform: translateX(2px);
}
#themeToggleBtn.on .toggle-handle {
  transform: translateX(26px);
  background: #fffde7;
}
#themeToggleBtn .toggle-icon {
  display: none;
}
@media (max-width: 600px) {
  #themeToggleBtn {
    top: 0.7rem;
    right: 0.7rem;
    width: 36px;
    height: 18px;
  }
  #themeToggleBtn .toggle-handle {
    width: 14px;
    height: 14px;
    transform: translateX(2px);
  }
  #themeToggleBtn.on .toggle-handle {
    transform: translateX(16px);
  }
}

/* Accessibility: focus outlines */
:focus-visible {
    outline: 2px solid #f9a825;
    outline-offset: 2px;
}

[data-theme="dark"] header h1 {
  color: #fff;
  text-shadow: 0 2px 12px rgba(0,0,0,0.25);
}
[data-theme="dark"] header p {
  color: #ffe082;
  text-shadow: 0 1px 8px rgba(0,0,0,0.18);
}
[data-theme="dark"] #themeToggleBtn.on .toggle-handle {
  background: #444950;
}

/* Practice page controls - scoped so .nav-btn (site nav) is not affected */
.practice-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem 1rem;
    justify-content: center;
    align-items: center;
    margin-top: 2rem;
}
.practice-controls .practice-btn {
    min-width: 88px;
    padding: 0.5rem 0.8rem;
    font-size: 1rem;
    border-radius: 10px;
    border: none;
    background: var(--color-primary);
    color: var(--color-btn-text);
    cursor: pointer;
    box-shadow: var(--color-btn-shadow);
}
.practice-controls label {
    margin-left: 0.25rem;
    margin-right: 0.25rem;
    font-size: 0.95rem;
}
.practice-controls input[type="number"] {
    width: 3.2em; /* keeps small but consistent */
    padding: 0.15rem 0.25rem;
    border-radius: 6px;
    border: 1px solid rgba(0,0,0,0.12);
}

/* Responsive layer: fluid typography and layout adjustments */
@media (min-width: 480px) and (max-width: 1200px) {
    :root {
        --fluid-type: calc(1rem + 0.2vw);
    }
    header h1 { font-size: clamp(1.6rem, 3.2vw, 2.4rem); }
    header p { font-size: clamp(1rem, 1.9vw, 1.25rem); }
    .container { padding: 1.5rem; }
}

@media (max-width: 600px) {
    .container { padding: 1rem; }
    header h1 { font-size: 1.4rem; }
    header p { font-size: 1rem; }
    .nav-grid { gap: 0.6rem; }
    .nav-btn { font-size: 15px; padding: 0.6rem 0.8rem; min-width: 100px; }
    .cheat-sheet-panel { width: 100vw; position: fixed; left: 0; }
    .footer-text { white-space: normal; text-align: center; }
}

@media (min-width: 900px) {
    .nav-grid { flex-direction: row; flex-wrap: wrap; justify-content: center; gap: 1rem; }
    .nav-btn { min-width: 160px; }
}