/* ============================================================
   Tiles Puzzle — main stylesheet
   ============================================================ */

[hidden] {
display: none;
}

:root {
--bg-1: #0d1b2a;
--bg-2: #132238;
--panel: rgba(14, 28, 45, 0.9);
--panel-strong: #10243a;
--line: rgba(244, 162, 97, 0.22);
--text: #edf2f4;
--muted: #b9c7d3;
--accent: #f4a261;
--accent-strong: #e76f51;
--link: #c9ecff;
--success: #2a9d8f;
--warning: #e9c46a;
--shadow: 0 22px 60px rgba(0, 0, 0, 0.33);
--radius: 18px;
--radius-sm: 12px;
--header-h: 56px;
--panel-w: 260px;
--font-display: "Gill Sans", "Trebuchet MS", "Avenir Next", sans-serif;
--font-body: "Segoe UI Variable Text", "Trebuchet MS", sans-serif;
}

*,
*::before,
*::after {
box-sizing: border-box;
}

html,
body {
min-height: 100%;
margin: 0;
background:
radial-gradient(circle at top left, rgba(244, 162, 97, 0.18), transparent 34%),
radial-gradient(circle at bottom right, rgba(42, 157, 143, 0.22), transparent 36%),
linear-gradient(160deg, var(--bg-1), var(--bg-2));
color: var(--text);
font-family: var(--font-body);
}

body {
overflow: hidden;
}

a:link,
a:visited {
color: var(--link);
}

a:hover,
a:focus-visible {
color: #ffffff;
text-decoration: underline;
text-underline-offset: 2px;
}

button,
input {
font: inherit;
}

button {
cursor: pointer;
}

summary {
cursor: pointer;
}

img {
display: block;
max-width: 100%;
}

figure.diagram {
   display: inline-block;
   max-width: 360px;
   border: 2px solid rgba(255, 255, 255, 0.86);
   border-radius: var(--radius);
   overflow: hidden;
   margin: 8px 0;
   vertical-align: top;
   background: rgba(255, 255, 255, 0.03);
}

figure.diagram img {
   width: 100%;
   display: block;
}

figure.diagram figcaption {
   background: var(--panel-strong);
   color: var(--muted);
   font-style: italic;
   font-size: 0.85rem;
   padding: 6px 10px;
}

.author-diagram {
   float: right;
   margin-left: 12px;
   width: 35%;
}

/* ---- App shell ---- */

.app-shell {
height: 100dvh;
display: flex;
flex-direction: column;
position: relative;
}

.app-header {
height: var(--header-h);
padding: 0 14px;
display: flex;
align-items: center;
gap: 12px;
backdrop-filter: blur(18px);
background: rgba(7, 16, 27, 0.65);
border-bottom: 1px solid rgba(255, 255, 255, 0.08);
position: relative;
z-index: 10;
}

.header-copy {
min-width: 0;
flex: 1;
display: flex;
flex-direction: column;
gap: 4px;
}

#app-header-title {
font-family: var(--font-display);
font-size: 1rem;
letter-spacing: 0.06em;
text-transform: uppercase;
}

#app-header-subtitle {
font-size: 0.85rem;
color: var(--muted);
}

.header-badge {
padding: 5px 10px;
border-radius: 999px;
border: 1px solid rgba(244, 162, 97, 0.3);
background: rgba(244, 162, 97, 0.12);
font-size: 0.78rem;
letter-spacing: 0.08em;
text-transform: uppercase;
white-space: nowrap;
}

.icon-btn {
width: 36px;
height: 36px;
border: 1px solid rgba(255, 255, 255, 0.12);
border-radius: 999px;
background: rgba(255, 255, 255, 0.05);
display: grid;
place-items: center;
color: var(--text);
transition: transform 0.2s ease, filter 0.2s ease;
}

.icon-btn:hover {
transform: translateY(-1px);
filter: brightness(1.06);
}

#app-content {
flex: 1;
overflow: auto;
padding: 14px;
}

.view {
max-width: 1260px;
margin: 0 auto;
}

.view-game {
height: 100%;
}

/* ---- Buttons ---- */

.btn {
display: inline-block;
border: none;
border-radius: 999px;
padding: 7px 18px;
background: linear-gradient(135deg, var(--accent), var(--accent-strong));
color: #101820;
font-weight: 600;
letter-spacing: 0.03em;
transition: transform 0.2s ease, filter 0.2s ease;
}

.btn:hover:not(:disabled) {
transform: translateY(-1px);
filter: brightness(1.06);
}

.btn:disabled {
opacity: 0.4;
cursor: not-allowed;
transform: none;
filter: none;
}

.btn-secondary {
background: rgba(255, 255, 255, 0.08);
color: var(--text);
border: 1px solid rgba(255, 255, 255, 0.12);
}

.btn-secondary.active {
background: rgba(244, 162, 97, 0.22);
border-color: rgba(244, 162, 97, 0.5);
color: var(--accent);
}

.btn-back {
margin-top: 8px;
align-self: flex-start;
}

/* ---- Game layout ---- */

.board-stage {
min-height: calc(100dvh - var(--header-h) - 40px);
display: grid;
grid-template-columns: minmax(0, 1fr) 220px;
gap: 18px;
align-items: start;
}

.board-left {
display: flex;
flex-direction: column;
gap: 10px;
min-width: 0;
}

.game-title {
font-family: var(--font-display);
font-size: 1rem;
letter-spacing: 0.08em;
text-transform: uppercase;
color: var(--accent);
margin: 0;
}

.board-sidebar {
display: flex;
flex-direction: column;
gap: 12px;
position: sticky;
top: 0;
}

/* ---- Upload section ---- */

.upload-section {
display: flex;
flex-direction: column;
gap: 4px;
}

.upload-label {
font-size: 0.82rem;
letter-spacing: 0.1em;
text-transform: uppercase;
color: var(--muted);
}

.upload-section input[type="file"] {
padding: 6px 10px;
border: 1px solid rgba(255, 255, 255, 0.14);
border-radius: var(--radius-sm);
background: rgba(255, 255, 255, 0.05);
color: var(--text);
cursor: pointer;
max-width: 100%;
}

.privacy-note {
font-size: 0.76rem;
color: var(--muted);
}

/* ---- Puzzle grid ---- */

.puzzle {
position: relative;
display: grid;
gap: 2px;
padding: 6px;
background: rgba(255, 255, 255, 0.04);
border: 1px solid rgba(255, 255, 255, 0.08);
border-radius: var(--radius);
box-shadow: var(--shadow);
max-width: 100%;
}

.puzzle::after {
content: "";
position: absolute;
inset: 0;
background-image: var(--full-image);
background-size: contain;
background-position: center;
background-repeat: no-repeat;
border-radius: calc(var(--radius) - 4px);
opacity: 0;
pointer-events: none;
transition: opacity 500ms ease;
}

.puzzle.solved::after {
opacity: 1;
}

.tile {
position: relative;
background-repeat: no-repeat;
cursor: pointer;
border-radius: 6px;
transition: transform 0.1s ease, opacity 500ms ease;
box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
}

.tile-number {
position: absolute;
bottom: 3px;
right: 5px;
font-size: 11px;
font-weight: bold;
color: white;
text-shadow: 0 1px 3px rgba(0, 0, 0, 0.85);
pointer-events: none;
user-select: none;
}

.puzzle.solved .tile {
opacity: 0;
}

@media (hover: hover) {
.tile:hover:not(.empty) {
transform: scale(0.95);
}
}

.tile.empty {
background-color: transparent;
cursor: default;
box-shadow: none;
}

.tile.movable {
cursor: grab;
box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25), 0 0 0 2px var(--accent) inset;
}

/* ---- Sidebar cards ---- */

.game-status-card {
padding: 10px 12px;
border-radius: 16px;
background: var(--panel);
border: 1px solid rgba(255, 255, 255, 0.08);
box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

#status {
margin: 0;
font-size: 0.9rem;
line-height: 1.45;
color: var(--text);
}

.moves-card {
padding: 10px 12px;
border-radius: 16px;
background: var(--panel);
border: 1px solid rgba(255, 255, 255, 0.08);
display: flex;
flex-direction: column;
gap: 6px;
}

#moves {
margin: 0;
font-size: 1rem;
font-weight: 700;
color: var(--accent);
}

.best-scores {
display: flex;
flex-direction: column;
gap: 2px;
}

#bestMovesToday,
#bestMovesAllTime {
margin: 0;
font-size: 0.84rem;
color: var(--muted);
}

.hint-text {
margin: 0;
font-size: 0.82rem;
color: var(--muted);
line-height: 1.4;
}

/* ---- View pages (Rules / Options / About) ---- */

.view-page:not([hidden]) {
display: flex;
flex-direction: column;
gap: 12px;
padding: 16px;
border-radius: var(--radius);
background: rgba(16, 36, 58, 0.84);
border: 1px solid rgba(255, 255, 255, 0.08);
box-shadow: var(--shadow);
}

.view-page h2 {
font-family: var(--font-display);
font-size: 1.2rem;
letter-spacing: 0.05em;
text-transform: uppercase;
margin: 0;
}

.view-page h3 {
font-family: var(--font-display);
font-size: 0.95rem;
letter-spacing: 0.06em;
text-transform: uppercase;
color: var(--accent);
margin: 4px 0 0;
}

.view-page p {
margin: 0;
font-size: 0.92rem;
line-height: 1.5;
}

.view-page details {
padding: 14px 16px;
border-radius: var(--radius-sm);
background: rgba(255, 255, 255, 0.04);
border: 1px solid rgba(255, 255, 255, 0.06);
}

.text-list {
margin: 12px 0 0;
padding-left: 18px;
display: grid;
gap: 8px;
font-size: 0.9rem;
}

/* ---- Options form ---- */

.options-form {
display: grid;
gap: 10px;
}

fieldset {
margin: 0;
padding: 10px 12px;
border-radius: var(--radius-sm);
border: 1px solid rgba(255, 255, 255, 0.1);
background: rgba(255, 255, 255, 0.03);
display: grid;
gap: 8px;
}

legend {
padding: 0 6px;
color: var(--accent);
font-size: 0.88rem;
}

.diff-row {
display: flex;
gap: 8px;
flex-wrap: wrap;
}

.diff-btn {
flex: 1 1 0;
min-width: 0;
border-radius: var(--radius-sm);
padding: 6px 10px;
}

.diff-btn.active {
background: linear-gradient(135deg, var(--accent), var(--accent-strong));
color: #101820;
}

.seed-row {
display: flex;
gap: 6px;
flex-wrap: wrap;
align-items: center;
}

#seedInput {
flex: 1 1 140px;
min-width: 0;
padding: 6px 10px;
border: 1px solid rgba(255, 255, 255, 0.14);
border-radius: var(--radius-sm);
background: rgba(255, 255, 255, 0.06);
color: var(--text);
}

#seedInput::placeholder {
color: var(--muted);
}

.highscore-grid {
display: grid;
grid-template-columns: minmax(0, 1fr) auto;
gap: 8px 12px;
align-items: center;
font-size: 0.9rem;
}

.highscore-grid p {
margin: 0;
}

/* ---- Focus styles ---- */

:focus-visible {
outline: 2px solid var(--accent);
outline-offset: 2px;
}

/* ---- Side panel ---- */

#panel-overlay {
position: fixed;
inset: 0;
background: rgba(0, 0, 0, 0.46);
z-index: 30;
}

#side-panel {
position: fixed;
left: 0;
top: 0;
bottom: 0;
width: var(--panel-w);
padding: 20px 0;
background: rgba(8, 17, 29, 0.98);
border-right: 1px solid rgba(255, 255, 255, 0.08);
transform: translateX(calc(-1 * var(--panel-w)));
transition: transform 0.25s ease;
z-index: 40;
}

#side-panel.open {
transform: translateX(0);
}

.panel-title {
padding: 0 20px 14px;
margin: 0;
font-family: var(--font-display);
letter-spacing: 0.08em;
text-transform: uppercase;
color: var(--muted);
}

.panel-nav {
list-style: none;
margin: 0;
padding: 0;
}

.panel-nav button {
width: 100%;
padding: 14px 20px;
background: transparent;
border: none;
color: var(--text);
text-align: left;
transition: background 0.2s ease;
}

.panel-nav button:hover {
background: rgba(255, 255, 255, 0.06);
}

.panel-divider {
height: 1px;
margin: 8px 0;
background: rgba(255, 255, 255, 0.08);
}

/* ---- Celebration canvas ---- */

.celebration-canvas {
position: fixed;
inset: 0;
width: 100dvw;
height: 100dvh;
max-width: 100dvw;
max-height: 100dvh;
pointer-events: none;
z-index: 9999;
display: none;
}

.celebration-canvas.active {
display: block;
}

/* ---- Responsive ---- */

@media (max-width: 980px) {
.board-stage {
grid-template-columns: 1fr;
}

.board-sidebar {
position: static;
flex-direction: row;
flex-wrap: wrap;
}

.board-sidebar > * {
flex: 1 1 180px;
min-width: 0;
}
}

@media (max-width: 720px) {
body {
overflow: auto;
}

   .author-diagram {
      float: none;
      margin-left: 0;
      width: 100%;
      max-width: 320px;
   }

#app-content {
padding: 10px;
}

.app-header {
padding: 0 12px;
gap: 10px;
}

#app-header-subtitle,
.header-badge {
display: none;
}

.board-stage {
gap: 12px;
}

.view-page,
.puzzle {
border-radius: 14px;
}

.diff-btn {
padding: 6px 8px;
font-size: 0.88rem;
}

#seedInput {
flex-basis: 100%;
}

#seedApplyBtn,
#seedClearBtn {
flex: 1 1 0;
}
}