@import url('https://fonts.googleapis.com/css2?family=Courier+Prime:ital,wght@0,400;0,700;1,400&family=Permanent+Marker&display=swap');
 
body {
    margin: 0; padding: 0;
    background-color: #e8e4dc; /* fallback if the texture is missing */
    background-image: url('White%20Crumpled%20Paper%20Texture.jpg');
    background-size: cover; background-attachment: fixed;
    font-family: 'Courier Prime', monospace; color: #333;
    display: flex; justify-content: center; align-items: center;
    min-height: 100vh; overflow: hidden;
}
 
nav {
    position: absolute; top: 16px; left: 16px;
    display: flex; gap: 8px; z-index: 1000; flex-wrap: wrap;
}
 
.paper-btn {
    background: #fdfbf7; border: 1px solid #ccc; padding: 8px 14px;
    font-family: 'Permanent Marker', cursive; font-size: 1rem;
    cursor: pointer; box-shadow: 2px 3px 5px rgba(0,0,0,0.2);
    transition: transform 0.5s;
    border-radius: 2px 255px 3px 25px / 255px 5px 225px 3px;
}
.paper-btn:hover { transform: scale(1.05) rotate(-2deg); }
.paper-btn:focus-visible { outline: 2px solid #333; outline-offset: 2px; }
.paper-btn[disabled] { opacity: 0.55; cursor: default; transform: none; }
 
/* The page you're currently on gets a marker underline. */
.paper-btn.is-current { border-bottom: 3px solid #333; }
 
.paper-btn.btn-quiet { font-size: 0.95rem; padding: 7px 12px; background: transparent; box-shadow: none; }
 
/* ---- Notebook sizing -------------------------------------------------
   Mobile: one page at a time, stacked top/bottom.
   The margin-top keeps the notebook clear of the floating nav buttons. */
#notebook {
    position: relative;
    width: 92vw; height: 74vh;
    margin-top: 56px;
    box-shadow: 5px 10px 25px rgba(0,0,0,0.4);
    border-radius: 5px 255px 10px 25px / 255px 5px 225px 10px;
    background: rgba(255, 255, 255, 1);
}
 
/* Base Mobile View: Vertical Flips (Notepad style) */
.static-page {
    position: absolute; width: 100%; height: 50%; box-sizing: border-box;
}
.static-page.left-top { top: 0; }
.static-page.right-bottom { bottom: 0; }
 
.flip-container {
    position: absolute; bottom: 0; width: 100%; height: 50%;
    perspective: 1500px; perspective-origin: center center;
}
.flip-container .flipper {
    position: relative; width: 100%; height: 100%;
    transform-style: preserve-3d; transition: transform 0.6s ease-in-out;
    transform-origin: 50% 0%; /* Pivots from the top center */
}
.flip-container.flip .flipper { transform: rotateX(180deg); }
 
.front, .back {
    position: absolute; width: 100%; height: 100%;
    backface-visibility: hidden; background-color: rgba(255, 255, 255, 1);
    box-sizing: border-box;
}
.front { transform: rotateX(0deg); }
.back { transform: rotateX(180deg); }
 
/* Desktop View: Horizontal Flips (Book style).
   min() lets the book grow to fill a large screen but shrink on a small
   laptop instead of overflowing. */
@media (min-width: 510px) {
    #notebook {
        width: min(1180px, 94vw);
        height: min(780px, 82vh);
        margin-top: 50px;
    }
 
    .static-page { width: 50%; height: 100%; }
    .static-page.left-top { top: 0; left: 0; }
    .static-page.right-bottom { bottom: auto; right: 0; top: 0; }
 
    .flip-container {
        width: 50%; height: 100%;
        bottom: auto; top: 0; right: 0;
    }
    .flip-container .flipper {
        transform-origin: 0% 50%; /* Pivots from the left center */
    }
    .flip-container.flip .flipper { transform: rotateY(-180deg); }
 
    .front { transform: rotateY(0deg); }
    .back { transform: rotateY(180deg); }
 
    nav { top: 20px; left: 20px; gap: 12px; }
    .paper-btn { font-size: 1.15rem; padding: 10px 18px; }
}
 
/* A bigger book deserves bigger type and more margin. */
@media (min-width: 1000px) {
    .page-content { padding: 56px 64px; }
    h1 { font-size: 2.3rem; }
    p, li { font-size: 1.05rem; }
    input, select { font-size: 1.15rem; }
}
 
@media (prefers-reduced-motion: reduce) {
    .flip-container .flipper { transition: none; }
    .paper-btn { transition: none; }
    .paper-btn:hover { transform: none; }
}
 
/* Pages hold more now, so let a long page scroll instead of spilling. */
.page-content {
    padding: 36px 40px; box-sizing: border-box; height: 100%;
    overflow-y: auto;
}
 
h1 {
    font-family: 'Permanent Marker', cursive; font-size: 1.9rem;
    margin-top: 0; margin-bottom: 16px;
    border-bottom: 2px dashed #999; padding-bottom: 10px;
}
h3 { font-family: 'Permanent Marker', cursive; font-weight: normal; margin-bottom: 4px; }
p { line-height: 1.5; }
.small { font-size: 0.85rem; }
.muted { color: #6b6b6b; }
 
.field { margin-bottom: 18px; }
 
label {
    display: block; font-size: 0.85rem; color: #555;
    margin-bottom: 4px; letter-spacing: 0.02em;
}
 
input, select {
    font-family: 'Courier Prime', monospace; background: transparent;
    border: none; border-bottom: 1px solid #333; width: 100%;
    margin-bottom: 0; font-size: 1.1rem; color: #333;
    padding: 2px 0; box-sizing: border-box;
}
input:focus, select:focus { outline: none; border-bottom: 2px solid #000; }
select { cursor: pointer; border-radius: 0; }
 
input.has-error { border-bottom: 2px solid #b03a2e; }
 
/* Red pen in the margin. */
.field-error {
    font-family: 'Permanent Marker', cursive;
    font-size: 0.82rem; color: #b03a2e;
    margin: 5px 0 0; line-height: 1.3;
}
 
.btn-row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; margin-top: 8px; }
 
/* Torn-off sticky note for the invoice explanation. */
.note {
    font-size: 0.85rem; line-height: 1.45; color: #444;
    background: #fdf6d8; border: 1px dashed #c9bb7a;
    padding: 10px 12px; margin: 4px 0 18px;
    border-radius: 1px 60px 2px 40px / 40px 2px 60px 2px;
}
 
.alert {
    font-size: 0.9rem; line-height: 1.45;
    padding: 10px 12px; margin-bottom: 14px;
    border-left: 4px solid #999; background: #f6f4ef;
}
.alert-bad  { border-left-color: #b03a2e; background: #fbeceb; }
.alert-ok   { border-left-color: #2e7d4f; background: #eaf5ee; }
.alert-wait { border-left-color: #b8860b; background: #fdf6e3; }
 
.lecture-list { padding-left: 20px; line-height: 1.6; }
 
.reg-list { list-style: none; padding: 0; margin: 0; }
.reg-list li {
    padding: 12px 0; border-bottom: 1px dashed #ccc;
}
.reg-list li:last-child { border-bottom: none; }
.reg-name { font-size: 1.05rem; font-weight: 700; }
 
.badge {
    display: inline-block; margin-top: 6px;
    font-size: 0.78rem; padding: 2px 10px;
    border: 1px solid currentColor;
    border-radius: 2px 40px 3px 30px / 30px 3px 40px 3px;
}
.badge-ok   { color: #2e7d4f; }
.badge-wait { color: #b8860b; }
 
/* ---- Mobile notice ---------------------------------------------------
   Tied to the same 510px breakpoint that switches the notebook from a
   two-page spread to a notepad, so it appears exactly when the layout
   degrades — not on a guess about the device. */
.mobile-note {
    position: fixed; left: 0; right: 0; bottom: 0; z-index: 2000;
    display: flex; align-items: center; gap: 10px;
    padding: 10px 12px;
    background: #fdf6d8; border-top: 1px dashed #c9bb7a;
    font-size: 0.8rem; line-height: 1.4; color: #444;
    box-shadow: 0 -2px 8px rgba(0,0,0,0.15);
}
.mobile-note-close {
    flex: none; background: none; border: none;
    font-size: 1.5rem; line-height: 1; color: #666;
    cursor: pointer; padding: 0 4px;
}
@media (min-width: 510px) {
    .mobile-note { display: none; }
}
 
/* 1. Force clicks to pass through the invisible main containers */
.flip-container {
    pointer-events: none;
}
 
/* 2. Re-enable clicks strictly on the physical page faces */
.front, .back {
    pointer-events: auto;
}
 
/* 3. Disable clicks on the front face when the page is flipped out of the way */
.flip-container.flip .front {
    pointer-events: none;
}
 
/* 4. Disable clicks on the back face when the page is resting on the right stack */
.flip-container:not(.flip) .back {
    pointer-events: none;
}