:root {
    color-scheme: dark light;

    --bg-body: #0f172a;
    --bg-panel: rgba(30, 41, 59, 0.72);
    --bg-input: rgba(15, 23, 42, 0.72);

    --border-subtle: rgba(255, 255, 255, 0.12);
    --border-strong: rgba(255, 255, 255, 0.2);

    --glass-shadow:
        0 8px 32px rgba(0, 0, 0, 0.28),
        inset 0 1px 1px rgba(255, 255, 255, 0.06);

    --border-focus: #10b981;

    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --text-soft: #cbd5e1;

    --primary: #10b981;
    --primary-hover: #059669;

    --secondary: rgba(255, 255, 255, 0.09);
    --secondary-hover: rgba(255, 255, 255, 0.16);

    --danger: #ef4444;

    --board-light: #ebecd0;
    --board-dark: #739552;

    --radius-sm: 5px;
    --radius-md: 8px;
    --radius-lg: 10px;

    --content-width: 1280px;
}


/* =========================================================
   LIGHT THEME
========================================================= */

@media (prefers-color-scheme: light) {

    :root {
        --bg-body: #eef2f3;
        --bg-panel: rgba(255, 255, 255, 0.78);
        --bg-input: rgba(255, 255, 255, 0.82);

        --border-subtle: rgba(15, 23, 42, 0.12);
        --border-strong: rgba(15, 23, 42, 0.2);

        --glass-shadow:
            0 8px 28px rgba(15, 23, 42, 0.12),
            inset 0 1px 1px rgba(255, 255, 255, 0.7);

        --text-main: #172033;
        --text-muted: #64748b;
        --text-soft: #334155;

        --secondary: rgba(15, 23, 42, 0.06);
        --secondary-hover: rgba(15, 23, 42, 0.11);
    }

    body {
        background-color: #eef2f3;
    }

    .main-header h1,
    h2,
    h3 {
        color: var(--text-main);
        text-shadow: none;
    }

    .piece.white {
        color: #ffffff;
    }

    input[type="text"],
    select {
        color: var(--text-main);
    }

    input::placeholder {
        color: rgba(15, 23, 42, 0.4);
    }

    .mode-button.active {
        color: var(--text-main);
    }

    .secondary-button,
    .icon-button {
        color: var(--text-main);
    }
}


/* =========================================================
   RESET
========================================================= */

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

html {
    min-height: 100%;
    scroll-behavior: smooth;
}

body {
    margin: 0;
    min-height: 100vh;

    background-color: var(--bg-body);

    background-image:
        linear-gradient(
            rgba(15, 23, 42, 0.48),
            rgba(15, 23, 42, 0.62)
        ),
        url("https://images.unsplash.com/photo-1529699211952-734e80c4d42b?q=70&w=1600&auto=format&fit=crop");

    background-size: cover;
    background-position: center;
    background-attachment: fixed;

    color: var(--text-main);

    font-family:
        Inter,
        ui-sans-serif,
        system-ui,
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        Roboto,
        Helvetica,
        Arial,
        sans-serif;

    line-height: 1.5;

    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;

    padding: 20px;
}

button,
input,
select {
    font: inherit;
}

button {
    cursor: pointer;
}

button:disabled {
    cursor: not-allowed;
    opacity: 0.55;
}

.hidden {
    display: none !important;
}


/* =========================================================
   PAGE
========================================================= */

.page-shell {
    width: 100%;
    max-width: var(--content-width);
    margin: 0 auto;
}

.main-header {
    margin-bottom: 24px;
    text-align: left;
}

.main-header h1 {
    margin: 0;

    display: flex;
    align-items: center;
    gap: 12px;

    font-size: clamp(24px, 3vw, 30px);
    font-weight: 800;

    color: #fff;

    text-shadow:
        0 2px 10px rgba(0, 0, 0, 0.5);
}

.chess-icon {
    color: var(--primary);
    font-size: 32px;
    line-height: 1;
}


/* =========================================================
   MAIN GRID
========================================================= */

.app-grid {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 360px;
    gap: 24px;
    align-items: start;
}


/* =========================================================
   PANELS
========================================================= */

.panel {
    background: var(--bg-panel);

    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);

    padding: 24px;

    box-shadow: var(--glass-shadow);
}

.panel + .panel {
    margin-top: 20px;
}

.panel-head {
    margin-bottom: 20px;
}

.label {
    margin: 0 0 4px;

    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.06em;

    font-weight: 700;

    color: var(--text-muted);
}

h2,
h3 {
    margin: 0;
}

h2 {
    font-size: 20px;
    font-weight: 700;
}

h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-main);
}


/* =========================================================
   BUTTONS
========================================================= */

button {
    border: none;
    border-radius: var(--radius-sm);

    display: inline-flex;
    align-items: center;
    justify-content: center;

    padding: 10px 16px;

    font-size: 14px;
    font-weight: 600;

    transition:
        background-color 0.16s ease,
        border-color 0.16s ease,
        transform 0.16s ease,
        box-shadow 0.16s ease;

    -webkit-tap-highlight-color: transparent;
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

.primary-button {
    width: 100%;

    padding: 12px;

    background: var(--primary);
    color: #fff;

    font-size: 15px;

    box-shadow:
        0 4px 12px rgba(16, 185, 129, 0.25);
}

.primary-button:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);

    box-shadow:
        0 6px 16px rgba(16, 185, 129, 0.3);
}

.secondary-button {
    background: var(--secondary);
    border: 1px solid var(--border-subtle);
    color: var(--text-main);
}

.secondary-button:hover {
    background: var(--secondary-hover);
    border-color: var(--border-strong);
}

.ghost-button {
    width: 100%;

    background: transparent;
    color: #ff5c5c;

    border: 1px solid rgba(255, 92, 92, 0.5);
}

.ghost-button:hover {
    background: rgba(255, 92, 92, 0.12);
    color: #ff7676;
}

.icon-button {
    min-width: 42px;

    background: var(--secondary);
    border: 1px solid var(--border-subtle);

    color: var(--text-main);
}

.icon-button:hover {
    background: var(--secondary-hover);
}


/* =========================================================
   HEADER TOOLBAR
========================================================= */

.board-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;

    gap: 16px;

    margin-bottom: 24px;
    padding-bottom: 16px;

    border-bottom: 1px solid var(--border-subtle);
}

.toolbar-actions {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}


/* =========================================================
   MODE SWITCHER
========================================================= */

.mode-switcher {
    display: flex;

    padding: 4px;
    margin-bottom: 20px;

    background: rgba(0, 0, 0, 0.16);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
}

.mode-button {
    flex: 1;

    padding: 8px;

    background: transparent;
    color: var(--text-muted);

    border: none;
}

.mode-button.active {
    background: var(--secondary-hover);
    color: var(--text-main);

    box-shadow:
        0 2px 8px rgba(0, 0, 0, 0.15);
}


/* =========================================================
   FORMS
========================================================= */

.field {
    display: flex;
    flex-direction: column;
    gap: 8px;

    margin-bottom: 20px;
}

.field span {
    font-size: 13px;
    font-weight: 500;
    color: var(--text-muted);
}

.field-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

input[type="text"],
select {
    width: 100%;

    background: var(--bg-input);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);

    color: var(--text-main);

    padding: 12px;

    outline: none;

    font-size: 14px;

    transition:
        border-color 0.16s ease,
        background-color 0.16s ease;
}

input[type="text"]:focus,
select:focus {
    border-color: var(--border-focus);
}

input::placeholder {
    color: rgba(255, 255, 255, 0.35);
}

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

.join-row input {
    flex: 1;
    min-width: 0;
}

.muted-copy {
    margin: 12px 0 0;

    font-size: 12px;
    color: var(--text-muted);

    text-align: center;
}


/* =========================================================
   CHESS BOARD
========================================================= */

.board-stage {
    width: 100%;
    max-width: 640px;

    margin: 0 auto;

    padding: 12px;

    background: rgba(0, 0, 0, 0.18);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);

    box-shadow:
        inset 0 2px 10px rgba(0, 0, 0, 0.35);
}

.board {
    width: 100%;
    aspect-ratio: 1 / 1;

    display: grid;

    grid-template-columns: repeat(8, 1fr);
    grid-template-rows: repeat(8, 1fr);

    overflow: hidden;

    border: 4px solid rgba(15, 23, 42, 0.8);
    border-radius: var(--radius-sm);

    contain: layout paint;
}

.square {
    width: 100%;
    height: 100%;

    position: relative;

    display: flex;
    align-items: center;
    justify-content: center;

    padding: 0;
    margin: 0;

    border: none;

    cursor: pointer;

    -webkit-tap-highlight-color: transparent;
}

.square.light {
    background-color: var(--board-light);
}

.square.dark {
    background-color: var(--board-dark);
}

.square.selected {
    background-color: rgba(234, 230, 93, 0.72);
}

.square.last-move {
    background-color: rgba(234, 230, 93, 0.42);
}

.square.check-square {
    background-color: rgba(239, 68, 68, 0.62);
}

.square.legal-target::after {
    content: "";

    position: absolute;

    width: 25%;
    height: 25%;

    border-radius: 50%;

    background: rgba(0, 0, 0, 0.25);

    pointer-events: none;
}

.square.capture-target::after {
    content: "";

    position: absolute;

    width: 80%;
    height: 80%;

    border-radius: 50%;

    border: 5px solid rgba(0, 0, 0, 0.25);

    background: transparent;

    pointer-events: none;
}

.piece {
    position: relative;
    z-index: 10;

    font-size: clamp(28px, 6vw, 65px);

    line-height: 1;

    user-select: none;
    pointer-events: none;
}

.piece.white {
    color: #fff;

    text-shadow:
        0 2px 4px rgba(0, 0, 0, 0.65);
}

.piece.black {
    color: #000;

    text-shadow:
        0 2px 4px rgba(255, 255, 255, 0.4);
}


/* =========================================================
   STATUS
========================================================= */

.status-strip {
    display: flex;
    justify-content: space-between;
    align-items: center;

    gap: 16px;

    margin-top: 24px;
    padding: 16px;

    background: var(--bg-panel);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
}

.status-message {
    margin: 0;

    font-size: 15px;
    font-weight: 500;
}

.status-meta {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    justify-content: flex-end;
}

.status-chip {
    padding: 4px 10px;

    border-radius: 20px;

    font-size: 12px;
    font-weight: 600;

    letter-spacing: 0.4px;
}

.turn-white {
    background: rgba(255, 255, 255, 0.9);
    color: #000;
}

.turn-black {
    background: rgba(0, 0, 0, 0.8);
    color: #fff;

    border: 1px solid var(--border-subtle);
}

.connection-solo {
    background: var(--secondary);
    color: var(--text-main);
}

.connection-party {
    background: var(--primary);
    color: #fff;
}


/* =========================================================
   PLAYERS
========================================================= */

.roster-grid {
    display: grid;
    grid-template-columns: 1fr;

    gap: 12px;

    margin-bottom: 20px;
}

.roster-card {
    display: flex;
    flex-direction: row;
    justify-content: space-between;
    align-items: center;

    gap: 12px;

    padding: 12px 16px;

    background: rgba(0, 0, 0, 0.16);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
}

.roster-card.white-player {
    border-left: 4px solid rgba(255, 255, 255, 0.8);
}

.roster-card.black-player {
    border-left: 4px solid rgba(0, 0, 0, 0.8);
}

.roster-info {
    display: flex;
    flex-direction: column;
    gap: 2px;

    min-width: 0;
}

.roster-role {
    font-size: 11px;

    text-transform: uppercase;

    color: var(--text-muted);
}

.roster-card strong {
    font-size: 14px;

    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.player-clock {
    min-width: 80px;

    padding: 6px 12px;

    background: rgba(0, 0, 0, 0.4);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);

    color: var(--text-main);

    font-family:
        ui-monospace,
        SFMono-Regular,
        Menlo,
        Monaco,
        Consolas,
        monospace;

    font-size: 20px;
    font-weight: 700;

    letter-spacing: 1px;

    text-align: center;

    transition:
        border-color 0.2s ease,
        background-color 0.2s ease;
}

.player-clock.active {
    background: rgba(16, 185, 129, 0.18);

    border-color: var(--primary);

    color: var(--primary);

    box-shadow:
        0 0 10px rgba(16, 185, 129, 0.25);
}

.player-clock.low {
    color: var(--danger);

    border-color: var(--danger);

    background: rgba(239, 68, 68, 0.1);
}


/* =========================================================
   SPECTATORS
========================================================= */

.spectator-header {
    display: flex;
    justify-content: space-between;
    align-items: center;

    margin-bottom: 8px;
}

.badge {
    padding: 2px 8px;

    background: var(--bg-input);

    border: 1px solid var(--border-subtle);
    border-radius: 12px;

    color: var(--text-muted);

    font-size: 11px;
    font-weight: 600;
}

.spectator-list {
    margin: 0;
    padding: 0;

    list-style: none;

    font-size: 13px;
    color: var(--text-muted);
}

.empty-state {
    font-style: italic;
    opacity: 0.7;
}


/* =========================================================
   MODAL
========================================================= */

.modal {
    position: fixed;
    inset: 0;

    z-index: 1000;

    display: flex;
    align-items: center;
    justify-content: center;

    padding: 20px;

    background: rgba(0, 0, 0, 0.62);

    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
}

.modal-card {
    width: min(100%, 420px);

    padding: 32px;

    background: var(--bg-panel);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);

    box-shadow: var(--glass-shadow);

    text-align: center;
}

.promotion-options {
    display: flex;
    justify-content: center;

    gap: 16px;

    margin-top: 24px;
}

.promotion-options button {
    padding: 16px;

    background: rgba(0, 0, 0, 0.25);

    border: 1px solid var(--border-subtle);

    color: #fff;

    font-size: 32px;
}

.promotion-options button:hover {
    background: var(--primary);
    border-color: var(--primary);
}


/* =========================================================
   TOAST
========================================================= */

.toast-host {
    position: fixed;

    right: 20px;
    bottom: 20px;

    z-index: 9999;

    display: flex;
    flex-direction: column;
    gap: 10px;

    max-width: min(420px, calc(100vw - 40px));
}

.toast {
    padding: 12px 20px;

    background: var(--bg-panel);

    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);

    color: var(--text-main);

    font-size: 14px;
    font-weight: 500;

    box-shadow:
        0 4px 12px rgba(0, 0, 0, 0.25);

    animation: slide-up 0.25s ease-out;
}

.toast.success {
    border-color: var(--primary);
}

.toast.error {
    border-color: var(--danger);
}

@keyframes slide-up {
    from {
        opacity: 0;
        transform: translateY(8px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}


/* =========================================================
   FOOTER
========================================================= */

.site-footer {
    margin-top: 28px;
    padding: 22px 8px 8px;

    border-top: 1px solid var(--border-subtle);

    display: flex;
    justify-content: center;
}

.repository-link {
    display: inline-flex;
    align-items: center;
    gap: 10px;

    padding: 8px 12px;

    color: var(--text-muted);

    text-decoration: none;

    border-radius: var(--radius-md);

    transition:
        color 0.16s ease,
        background-color 0.16s ease,
        transform 0.16s ease;
}

.repository-link:hover {
    color: var(--text-main);
    background: var(--secondary);

    transform: translateY(-1px);
}

.repository-logo {
    display: block;

    width: 34px;
    height: 34px;

    object-fit: contain;

    border-radius: 7px;
}

.repository-name {
    font-size: 13px;
    font-weight: 600;
}


/* =========================================================
   RESPONSIVE
========================================================= */

@media (max-width: 960px) {

    body {
        padding: 14px;
    }

    .app-grid {
        grid-template-columns: 1fr;
    }

    .board-toolbar {
        flex-direction: column;
        align-items: stretch;
    }

    .toolbar-actions {
        width: 100%;
    }

    .toolbar-actions button {
        flex: 1;
    }
}


@media (max-width: 600px) {

    body {
        padding: 10px;
    }

    .main-header {
        margin-bottom: 16px;
    }

    .main-header h1 {
        font-size: 24px;
    }

    .chess-icon {
        font-size: 28px;
    }

    .panel {
        padding: 16px;
    }

    .app-grid {
        gap: 14px;
    }

    .board-stage {
        padding: 6px;
    }

    .board {
        border-width: 3px;
    }

    .piece {
        font-size: clamp(25px, 11vw, 50px);
    }

    .status-strip {
        flex-direction: column;
        align-items: stretch;
    }

    .status-meta {
        justify-content: flex-start;
    }

    .field-grid {
        grid-template-columns: 1fr;
        gap: 0;
    }

    .toolbar-actions {
        display: grid;
        grid-template-columns: 1fr 1fr;
    }

    #copyInviteButton {
        grid-column: span 2;
    }

    .join-row {
        flex-direction: column;
    }

    .toast-host {
        right: 10px;
        bottom: 10px;

        max-width: calc(100vw - 20px);
    }
}


@media (max-width: 380px) {

    .panel {
        padding: 12px;
    }

    .toolbar-actions {
        grid-template-columns: 1fr;
    }

    #copyInviteButton {
        grid-column: auto;
    }

    .player-clock {
        min-width: 70px;
        font-size: 17px;
    }
}


/* =========================================================
   REDUCED MOTION
========================================================= */

@media (prefers-reduced-motion: reduce) {

    *,
    *::before,
    *::after {
        scroll-behavior: auto !important;
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}


/* =========================================================
   LOW POWER / TOUCH DEVICES
========================================================= */

@media (hover: none) {

    .primary-button:hover,
    .secondary-button:hover,
    .ghost-button:hover,
    .icon-button:hover,
    .repository-link:hover {
        transform: none;
    }
}