:root {
    --bg-color: #0f172a;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-color: #38bdf8;
    --accent-hover: #0ea5e9;
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -1px rgba(0, 0, 0, 0.15);

    --board-size: min(80vw, 500px);
    --gap: 4px;
    --piece-size: calc((var(--board-size) - (var(--gap) * 2)) / 3);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    background-image:
        radial-gradient(at 0% 0%, rgba(56, 189, 248, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(139, 92, 246, 0.15) 0px, transparent 50%);
    background-attachment: fixed;
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow-x: hidden;
}

.app-container {
    width: 100%;
    max-width: 800px;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2rem;
}

header {
    text-align: center;
    animation: fadeDown 0.8s ease-out;
}

header h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    letter-spacing: -1px;
}

.accent {
    color: var(--accent-color);
    text-shadow: 0 0 20px rgba(56, 189, 248, 0.4);
}

header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Glass Panel Utilities */
.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 1.5rem;
    box-shadow: var(--glass-shadow);
    padding: 2rem;
}

.glass-panel-sm {
    background: var(--glass-bg);
    backdrop-filter: blur(8px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 0.75rem 1.5rem;
}

/* Buttons */
button {
    cursor: pointer;
    font-family: inherit;
    border: none;
    transition: all 0.2s ease;
}

.primary-btn {
    background: var(--accent-color);
    color: #0f172a;
    font-weight: 700;
    padding: 0.75rem 2rem;
    border-radius: 99px;
    font-size: 1rem;
    box-shadow: 0 0 15px rgba(56, 189, 248, 0.3);
}

.primary-btn:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 0 25px rgba(56, 189, 248, 0.5);
}

.secondary-btn {
    background: transparent;
    border: 1px solid var(--glass-border);
    color: var(--text-secondary);
    padding: 0.6rem 1.5rem;
    border-radius: 99px;
    font-size: 0.9rem;
}

.secondary-btn:hover {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
}

.icon-btn {
    background: transparent;
    color: var(--text-secondary);
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--accent-color);
    transform: rotate(15deg);
}

/* Upload Zone */
#upload-zone {
    width: 100%;
    max-width: 500px;
    min-height: 300px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    transition: all 0.3s ease;
    border: 2px dashed var(--glass-border);
}

#upload-zone:hover,
#upload-zone.dragover {
    border-color: var(--accent-color);
    background: rgba(56, 189, 248, 0.05);
}

.upload-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    color: var(--text-secondary);
}

.upload-content svg {
    color: var(--accent-color);
    margin-bottom: 0.5rem;
}

/* Game Area */
#game-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
    width: 100%;
    animation: fadeUp 0.6s ease-out;
}

.game-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    max-width: var(--board-size);
}

.stat {
    display: flex;
    gap: 0.5rem;
    align-items: baseline;
}

.stat .label {
    text-transform: uppercase;
    font-size: 0.75rem;
    letter-spacing: 1px;
    color: var(--text-secondary);
}

.stat .value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-color);
    font-feature-settings: "tnum";
}

/* Board */
.board {
    /* Dynamic width/height will be set by JS */
    /* --board-size, --piece-size removed from here as they are dynamic now */
    position: relative;
    background: rgba(255, 255, 255, 0.03);
    border-radius: 12px;
    box-shadow: inset 0 0 20px rgba(0, 0, 0, 0.3);
    user-select: none;
    touch-action: none;

    /* Center it visually */
    margin: 0 auto;
    transition: width 0.3s ease, height 0.3s ease;
}

.piece {
    /* Absolute is REQUIRED for free dragging */
    position: absolute;
    top: 0;
    left: 0;

    /* Width/Height set by JS now */
    /* width: var(--piece-size); */
    /* height: var(--piece-size); */

    background-size: var(--board-size) var(--board-size);
    border-radius: 8px;
    cursor: grab;

    /* Hardware acceleration for smooth drag */
    will-change: transform;
    transition: transform 0.1s linear;
    /* Fast for drag, JS handles non-linear if needed */
    /* Note: We essentially disable CSS transition during drag in JS usually, 
       but for "follow" it's better to have 0 transition or very fast one. 
       Let's use 0.1s for smooth follow, or 0 for instant. JS updates every frame.
    */
    transition: transform 0.05s linear;

    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    overflow: hidden;
}

.piece:hover {
    z-index: 10;
    box-shadow: 0 0 0 2px var(--accent-color), 0 8px 15px rgba(0, 0, 0, 0.5);
}

.piece:active {
    cursor: grabbing;
    transform: scale(0.95);
}

/* Dragging State */
.piece.dragging {
    opacity: 0.9;
    /* Make it more visible */
    border: 2px solid var(--accent-color);
    box-shadow: 0 0 20px rgba(56, 189, 248, 0.6);
    z-index: 1000 !important;
    /* Always on top */
    cursor: grabbing;

    /* CRITICAL: No lag while dragging */
    transition: none !important;
    will-change: transform;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 100;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.modal.visible {
    opacity: 1;
    pointer-events: auto;
}

.modal-content {
    text-align: center;
    transform: translateY(20px);
    transition: transform 0.3s ease;
    min-width: 300px;
}

.modal.visible .modal-content {
    transform: translateY(0);
}

.hidden {
    display: none !important;
}

/* Animations */
@keyframes fadeDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

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

@keyframes fadeUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

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

#fireworks-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 999;
}

@media (max-width: 600px) {
    header h1 {
        font-size: 2rem;
    }

    .app-container {
        padding: 1rem;
    }
}

/* Modal Overlay */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal.hidden {
    display: none !important;
}

.modal-content {
    text-align: center;
    max-width: 90%;
}