:root {
    --bg-color: #0D1B2A;
    --element-bg: #1B263B;
    --element-border: #415A77;
    --text-color: #E0E1DD;
    --accent-color: #778DA9;
    --panel-bg: #1c2a3eef; /* Slightly transparent for backdrop filter */
    --panel-border: #415A77;

    --alkali-metal: #FF6B6B;
    --alkaline-earth-metal: #FFD166;
    --transition-metal: #06D6A0;
    --lanthanide: #118AB2;
    --actinide: #073B4C;
    --post-transition-metal: #788bff;
    --metalloid: #BFB0D3;
    --halogen: #F78154;
    --noble-gas: #9B5DE5;
    --diatomic-nonmetal: #4CAF50; /* Green for nonmetals */
    --polyatomic-nonmetal: #388E3C; /* Darker Green */
    --unknown: #6c757d;

    /* Define variable for new element size if needed */
    --new-element-min-height-mobile: 80px;
    --new-element-min-height-desktop: 90px;
}

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

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    overscroll-behavior-y: contain; /* Prevents pull-to-refresh on mobile */
}

#splash-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--bg-color), var(--element-bg)); /* Modern gradient */
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000; /* Ensure it's on top */
    opacity: 1;
    visibility: visible;
    transform: scale(1); /* Initial scale */
    transition: opacity 0.6s ease-out, visibility 0.6s ease-out, transform 0.6s ease-in-out; /* Smooth fade-out and scale */
}

#splash-screen.hidden {
    opacity: 0;
    visibility: hidden;
    transform: scale(0.9); /* Scale down slightly on hide */
    pointer-events: none; /* Make it unclickable when hidden */
}

.splash-content {
    text-align: center;
    padding: 20px;
    /* Added to center the image and text vertically */
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 90%; /* Constrain width slightly */
    max-width: 500px; /* Max width for the content area */
}

#splash-image {
    display: block; /* Ensure image is block level */
    width: 100%; /* Make image responsive */
    max-width: 300px; /* Limit max size of image */
    height: auto; /* Maintain aspect ratio */
    margin-bottom: 20px; /* Space between image and subtitle */
    border-radius: 15px; /* Slightly rounded corners */
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.4); /* Add some shadow */
}

.splash-subtitle {
    font-size: clamp(0.8rem, 3vw, 1.2rem);
    color: var(--accent-color);
    font-weight: 300;
    /* Removed margin-top as spacing is handled by image margin-bottom */
}

header {
    text-align: center;
    padding: 20px 10px;
    background-color: var(--element-bg);
    margin-bottom: 20px;
    border-bottom: 2px solid var(--accent-color);
    position: relative; /* For settings button positioning */
}

header h1 {
    font-size: clamp(1.8rem, 5vw, 2.5rem);
    margin-bottom: 5px;
    color: var(--text-color);
}

header p {
    font-size: clamp(0.9rem, 2.5vw, 1.1rem);
    color: var(--accent-color);
}

#settings-button {
    position: absolute;
    top: 15px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 1.8rem;
    cursor: pointer;
    padding: 5px;
    line-height: 1;
    transition: transform 0.2s ease, color 0.2s ease;
}

#settings-button:hover {
    transform: rotate(30deg);
    color: var(--accent-color);
}

#periodic-table-container {
    width: 100%;
    overflow-x: auto; /* Allows horizontal scrolling on small screens */
    padding: 10px;
}

#periodic-table {
    display: grid;
    grid-template-columns: repeat(18, minmax(50px, 1fr)); /* minmax for responsive cells */
    /* Updated grid-template-rows to explicitly define rows up to 12, making rows 11 and 12 larger */
    grid-template-rows: repeat(7, minmax(60px, 1fr)) /* Rows 1-7 (main table) */
                        repeat(2, minmax(0, 1fr))    /* Rows 8-9 (placeholder for L/A) */
                        minmax(60px, 1fr)             /* Row 10 (L/A block starts) */
                        repeat(2, minmax(var(--new-element-min-height-mobile), 1fr)); /* Rows 11-12 (new elements) */
    gap: 5px;
    min-width: 950px; /* (18 * 50px) + (17 * 5px) for gaps approx */
    margin: 0 auto;
    padding-bottom: 20px; /* Space for scrollbar if needed */
    /* Added perspective for 3D-like transforms if desired, optional */
    /* perspective: 1000px; */
}

.element-cell {
    background-color: var(--element-bg);
    border: 1px solid var(--element-border);
    border-radius: 8px;
    padding: 5px;
    text-align: center;
    cursor: pointer;
    /* Updated transition to include opacity and transform for appear animation */
    transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275), /* Added bounce */
                box-shadow 0.2s ease-out,
                background-color 0.2s ease-out,
                opacity 0.4s ease-out;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    box-shadow: 0 2px 4px rgba(0,0,0,0.3), inset 0 1px 2px rgba(255,255,255,0.05);
    font-size: 0.7rem; /* Smaller base font size for tiles */
    position: relative; /* Needed for absolute positioning of number */
    /* Initial state for appear animation - set via JS now */
    /* opacity: 0; */
    /* transform: scale(0.5); */
}

.element-cell:hover {
    transform: scale(1.08); /* Keep hover slightly smaller than select */
    box-shadow: 0 5px 15px rgba(0,0,0,0.5), 0 0 15px var(--category-color, var(--accent-color));
    z-index: 10;
    position: relative; /* To ensure it's above others */
}

.element-cell.selected {
    transform: scale(1.1); /* Keep selected scale */
    box-shadow: 0 0 20px var(--category-color, var(--accent-color)), 0 0 30px var(--category-color, var(--accent-color));
    border-width: 2px;
    z-index: 11;
}

.element-cell.popup-active {
    animation: elementPopup 0.8s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
    z-index: 100;
}

@keyframes elementPopup {
    0% { transform: scale(1.1) rotateY(0deg); }
    35% { transform: scale(1.5) rotateY(180deg); }
    45% { transform: scale(1.5) rotateY(180deg); }
    100% { transform: scale(1.1) rotateY(360deg); }
}

.particles-container {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: -1;
}

.particle {
    position: absolute;
    background-color: var(--category-color, var(--accent-color));
    border-radius: 50%;
    opacity: 0.8;
    pointer-events: none;
    z-index: 200;
}

.element-cell.active-effect::before {
    content: '';
    position: absolute;
    top: -10px;
    left: -10px;
    right: -10px;
    bottom: -10px;
    border-radius: 15px;
    background: radial-gradient(circle, var(--category-color, var(--accent-color)) 0%, transparent 70%);
    opacity: 0;
    z-index: -1;
    animation: pulsate 1s ease-out infinite;
}

@keyframes pulsate {
    0% { transform: scale(0.95); opacity: 0; }
    50% { opacity: 0.5; }
    100% { transform: scale(1.1); opacity: 0; }
}

.element-cell .atomic-number {
    font-size: 0.7em;
    position: absolute;
    top: 3px;
    left: 4px;
    opacity: 0.7;
}

.element-cell .symbol {
    font-size: 1.5em;
    font-weight: bold;
    line-height: 1;
}

.element-cell .name {
    font-size: 0.6em;
    margin-top: 2px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    width: 90%;
}

/* Category specific styles */
.element-cell.alkali-metal { --category-color: var(--alkali-metal); border-color: var(--alkali-metal); }
.element-cell.alkaline-earth-metal { --category-color: var(--alkaline-earth-metal); border-color: var(--alkaline-earth-metal); }
.element-cell.transition-metal { --category-color: var(--transition-metal); border-color: var(--transition-metal); }
.element-cell.lanthanide { --category-color: var(--lanthanide); border-color: var(--lanthanide); }
.element-cell.actinide { --category-color: var(--actinide); border-color: var(--actinide); }
.element-cell.post-transition-metal { --category-color: var(--post-transition-metal); border-color: var(--post-transition-metal); }
.element-cell.metalloid { --category-color: var(--metalloid); border-color: var(--metalloid); }
.element-cell.halogen { --category-color: var(--halogen); border-color: var(--halogen); }
.element-cell.noble-gas { --category-color: var(--noble-gas); border-color: var(--noble-gas); }
.element-cell.diatomic-nonmetal { --category-color: var(--diatomic-nonmetal); border-color: var(--diatomic-nonmetal); }
.element-cell.polyatomic-nonmetal { --category-color: var(--polyatomic-nonmetal); border-color: var(--polyatomic-nonmetal); }
.element-cell.unknown { --category-color: var(--unknown); border-color: var(--unknown); }

.creator-credit {
    grid-column: 3 / 10;
    grid-row: 2;
    display: flex;
    justify-content: center;
    align-items: center;
    background: transparent;
    border: none;
    color: rgba(180, 180, 180, 0.4);
    font-size: 0.9rem;
    text-decoration: none;
    cursor: pointer;
    transition: color 0.3s ease, opacity 0.3s ease;
    z-index: 5;
    padding: 5px;
}

.creator-credit:hover {
    color: rgba(220, 220, 220, 0.7);
    text-decoration: underline;
}

#element-detail-panel, #settings-panel {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    max-height: 75vh; /* Max height on mobile */
    background-color: var(--panel-bg);
    backdrop-filter: blur(10px) saturate(150%);
    -webkit-backdrop-filter: blur(10px) saturate(150%);
    border-top: 2px solid var(--panel-border);
    border-top-left-radius: 20px;
    border-top-right-radius: 20px;
    box-shadow: 0 -5px 20px rgba(0,0,0,0.3);
    padding: 20px;
    padding-top: 40px; /* Space for close button */
    overflow-y: auto;
    z-index: 100;
    transform: translateY(100%);
    transition: transform 0.4s cubic-bezier(0.25, 0.8, 0.25, 1);
}

#element-detail-panel.visible, #settings-panel.visible {
    transform: translateY(0);
}

#element-detail-panel.hidden, #settings-panel.hidden {
    transform: translateY(100%);
}

#close-panel-button, #close-settings-button {
    position: absolute;
    top: 10px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 2rem;
    cursor: pointer;
    padding: 5px;
    line-height: 1;
}

#detail-content h2, .settings-content h2 {
    font-size: 1.8rem;
    margin-bottom: 15px;
    color: var(--category-color, var(--accent-color)); /* Will be set by JS */
    text-align: center;
}

#detail-content p {
    margin-bottom: 10px;
    font-size: 0.95rem;
    line-height: 1.7;
}

#detail-content strong {
    color: var(--accent-color);
    min-width: 120px;
    display: inline-block;
}

#detail-content .summary {
    margin-top: 15px;
    font-style: italic;
    opacity: 0.9;
}

.settings-content {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 15px;
    padding-top: 20px; /* Offset for close button */
}

.settings-content h2 {
    color: var(--accent-color);
    width: 100%;
}

.setting-item {
    display: flex;
    align-items: center;
    width: 100%;
}

.setting-item input[type="radio"] {
    margin-right: 10px;
    appearance: none;
    -webkit-appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    border: 2px solid var(--accent-color);
    outline: none;
    cursor: pointer;
    position: relative;
    flex-shrink: 0;
}

.setting-item input[type="radio"]:checked {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
}

.setting-item input[type="radio"]:checked::before {
    content: '';
    display: block;
    width: 10px;
    height: 10px;
    background-color: var(--text-color);
    border-radius: 50%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.setting-item label {
    font-size: 1rem;
    cursor: pointer;
}

/* Dim other elements when one is selected - only apply AFTER initial animation */
body.element-selected.animation-complete #periodic-table .element-cell:not(.selected) {
    opacity: 0.5;
    transform: scale(0.95);
}

/* Hold Animation Styles */
.element-cell.being-held {
    z-index: 50;
    /* transform controlled by JS for dynamic scaling */
}

.orbital-container {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 5;
}

.orbital-particle {
    position: absolute;
    top: 50%;
    left: 50%;
    border-radius: 50%;
    transform: translate(-50%, -50%);
    pointer-events: none;
    animation: orbit 2s linear infinite;
}

@keyframes orbit {
    0% {
        transform: translate(-50%, -50%) rotate(0deg) translateX(20px) rotate(0deg);
    }
    100% {
        transform: translate(-50%, -50%) rotate(360deg) translateX(20px) rotate(-360deg);
    }
}

.energy-field {
    position: absolute;
    top: -4px;
    left: -4px;
    right: -4px;
    bottom: -4px;
    border: 2px solid;
    border-radius: 10px;
    opacity: 0;
    pointer-events: none;
    animation: energyPulse 1.5s ease-in-out infinite;
}

@keyframes energyPulse {
    0%, 100% {
        opacity: 0.2;
        transform: scale(1);
    }
    50% {
        opacity: 0.5;
        transform: scale(1.05);
    }
}

.inner-glow {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    border-radius: 8px;
    opacity: 0.3;
    pointer-events: none;
}

/* Make sure hold animations work well with existing animations */
.element-cell.being-held:not(.popup-active) {
    animation: none; /* Prevent popup animation during hold */
}

.element-cell.being-held .orbital-particle:nth-child(odd) {
    animation-direction: reverse; /* Alternate direction for visual variety */
}

.element-cell.being-held .orbital-particle:nth-child(3n) {
    animation-duration: 2.5s; /* Vary speeds */
}

.element-cell.being-held .orbital-particle:nth-child(3n+1) {
    animation-duration: 1.8s; /* More speed variation */
}

/* Mobile optimizations for hold animation */
@media (max-width: 767px) {
    .orbital-particle {
        animation: orbit 1.5s linear infinite; /* Slightly faster on mobile */
    }
}

/* Desktop styling adjustments */
@media (min-width: 768px) {
    #periodic-table {
        grid-template-columns: repeat(18, minmax(60px, 1fr));
        /* Updated grid-template-rows for desktop */
        grid-template-rows: repeat(7, minmax(70px, 1fr)) /* Rows 1-7 (main table) */
                            repeat(2, minmax(0, 1fr))    /* Rows 8-9 (placeholder for L/A) */
                            minmax(70px, 1fr)             /* Row 10 (L/A block starts) */
                            repeat(2, minmax(var(--new-element-min-height-desktop), 1fr)); /* Rows 11-12 (new elements) */
        gap: 6px;
        max-width: 1200px; /* Ensure it doesn't get too wide */
    }

    .element-cell {
        font-size: 0.8rem;
    }
    .element-cell .symbol {
        font-size: 1.7em;
    }
    .element-cell .name {
        font-size: 0.7em;
    }

    #element-detail-panel, #settings-panel {
        width: 400px;
        max-height: 90vh;
        left: auto;
        right: 20px;
        bottom: 20px;
        top: auto; /* Override fixed bottom: 0 */
        border-radius: 15px;
        border: 2px solid var(--panel-border);
        transform: translateX(120%); /* Slide from right */
    }

    #element-detail-panel.visible, #settings-panel.visible {
        transform: translateX(0);
    }
    #element-detail-panel.hidden, #settings-panel.hidden {
        transform: translateX(120%);
    }

    /* Adjust settings panel specific position/size for desktop */
    #settings-panel {
        top: 80px; /* Position higher than detail panel */
        max-height: 50vh; /* Shorter than detail panel */
        width: 350px; /* Slightly narrower */
        padding-top: 20px;
    }
}

@media (min-width: 1200px) {
     #periodic-table {
        gap: 8px;
    }
}

/* For elements with no specific data, to avoid empty cells */
.element-cell.empty {
    background-color: transparent;
    border: none;
    box-shadow: none;
    pointer-events: none; /* Make them unclickable */
}