:root {
    --bg-color: #f0f4f8;
    --text-color: #333;
    --card-bg: #ffffff;
    --primary-color: #FF6B6B;
    --secondary-color: #4ECDC4;
    --accent-color: #FFE66D;
    --font-main: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-fun: 'ZCOOL KuaiLe', cursive;
    /* Google Font for Chinese fun style */
}

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    width: 100%;
    text-align: center;
}

header {
    margin-bottom: 30px;
}

header h1 {
    font-family: var(--font-fun);
    font-size: 3rem;
    color: var(--primary-color);
    text-shadow: 2px 2px 0px var(--accent-color);
    margin-bottom: 10px;
}

header p {
    font-size: 1.2rem;
    color: #666;
}

/* Periodic Table Grid */
.periodic-table {
    display: grid;
    grid-template-columns: repeat(18, 1fr);
    gap: 8px;
    padding: 20px;
    background: white;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    overflow-x: auto;
    /* For smaller screens */
}

.element-card {
    aspect-ratio: 1;
    background-color: var(--card-bg);
    border-radius: 8px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    border: 2px solid transparent;
    position: relative;
    user-select: none;
}

.element-card:hover {
    transform: scale(1.1);
    z-index: 10;
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.2);
    border-color: var(--text-color);
}

.element-number {
    font-size: 0.7rem;
    position: absolute;
    top: 4px;
    left: 4px;
    opacity: 0.7;
}

.element-symbol {
    font-size: 1.4rem;
    font-weight: bold;
    font-family: var(--font-fun);
}

.element-name {
    font-size: 0.6rem;
    margin-top: 2px;
}

/* Categories Colors */
.cat-alkali {
    background-color: #FF9AA2;
}

/* Red-ish */
.cat-alkaline {
    background-color: #FFB7B2;
}

/* Orange-ish */
.cat-transition {
    background-color: #FFDAC1;
}

/* Peach */
.cat-basic {
    background-color: #E2F0CB;
}

/* Green-ish */
.cat-metalloid {
    background-color: #B5EAD7;
}

/* Mint */
.cat-nonmetal {
    background-color: #C7CEEA;
}

/* Blue-ish */
.cat-halogen {
    background-color: #F6EAC2;
}

/* Yellow-ish */
.cat-noble {
    background-color: #E2F0CB;
}

/* Light Green */
.cat-lanthanide {
    background-color: #FF9AA2;
}

.cat-actinide {
    background-color: #FFB7B2;
}

/* Empty cells for spacing */
.empty-cell {
    visibility: hidden;
}

/* Modal Styles */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s;
}

.modal.show {
    opacity: 1;
    pointer-events: all;
}

.modal-content {
    background-color: white;
    padding: 30px;
    border-radius: 20px;
    width: 90%;
    max-width: 500px;
    text-align: left;
    position: relative;
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.3);
    animation: popIn 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

@keyframes popIn {
    from {
        transform: scale(0.8);
        opacity: 0;
    }

    to {
        transform: scale(1);
        opacity: 1;
    }
}

.close-btn {
    position: absolute;
    top: 15px;
    right: 20px;
    font-size: 2rem;
    cursor: pointer;
    color: #aaa;
}

.close-btn:hover {
    color: #333;
}

.modal-header {
    text-align: center;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px dashed #eee;
}

#modal-symbol {
    font-size: 4rem;
    margin: 0;
    font-family: var(--font-fun);
    color: var(--primary-color);
}

#modal-name {
    margin: 0;
    font-size: 1.5rem;
    color: #555;
}

.fun-fact-box {
    background-color: #FFF9C4;
    padding: 15px;
    border-radius: 10px;
    margin-top: 20px;
    border: 2px solid #FBC02D;
}

.fun-fact-box h4 {
    margin-top: 0;
    color: #F57F17;
}

.pinyin {
    font-size: 1rem;
    color: #888;
    font-weight: normal;
    margin-left: 10px;
    font-family: var(--font-main);
}

.placeholder {
    background-color: #eee;
    cursor: default;
    border: none;
}

.placeholder:hover {
    transform: none;
    box-shadow: none;
}

.hidden {
    display: none;
}