:root {
    /* Light Mode - Cute Pastel Green Palette */
    --bg-gradient: linear-gradient(135deg, #e8f5e9 0%, #c8e6c9 100%);
    --bg-color: #c8e6c9;
    --text-color: #2e4a3b;
    --primary-color: #81c784;
    --primary-hover: #66bb6a;
    --secondary-color: #a5d6a7;
    --card-bg: rgba(255, 255, 255, 0.45);
    --card-border: rgba(255, 255, 255, 0.6);
    --shadow-color: rgba(129, 199, 132, 0.15);
    
    /* Animation Speeds */
    --transition-speed: 0.3s;
}

[data-theme="dark"] {
    /* Dark Mode - Dreamy Night Kitty Palette (Green version) */
    --bg-gradient: linear-gradient(135deg, #1b2e20 0%, #152219 100%);
    --bg-color: #152219;
    --text-color: #e8f5e9;
    --primary-color: #66bb6a;
    --primary-hover: #81c784;
    --secondary-color: #2e4a3b;
    --card-bg: rgba(27, 46, 32, 0.5);
    --card-border: rgba(255, 255, 255, 0.1);
    --shadow-color: rgba(0, 0, 0, 0.25);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

body {
    font-family: 'Nunito', sans-serif;
    background: var(--bg-color);
    background-image: var(--bg-gradient);
    color: var(--text-color);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Glassmorphism Header */
.glass-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 5%;
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--card-border);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo h1 {
    font-family: 'Pacifico', cursive;
    font-size: 1.8rem;
    color: var(--primary-color);
    text-shadow: 1px 1px 2px var(--shadow-color);
}

.paw-icon {
    font-size: 1.8rem;
    animation: wave 3s infinite ease-in-out;
    display: inline-block;
}

/* Theme Toggle Button */
.btn-icon {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 50%;
    width: 45px;
    height: 45px;
    font-size: 1.5rem;
    cursor: pointer;
    box-shadow: 0 4px 6px var(--shadow-color);
    display: flex;
    justify-content: center;
    align-items: center;
}

.btn-icon:hover {
    transform: scale(1.1) rotate(15deg);
}

/* Main Content */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 5%;
}

h2 {
    font-family: 'Pacifico', cursive;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* Hero Section */
.hero {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 2rem;
    padding: 3rem 0;
}

.hero-content {
    flex: 1;
}

.title-primary {
    font-size: 3.5rem;
    line-height: 1.2;
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    font-weight: 600;
    opacity: 0.9;
}

/* Buttons */
.btn-primary, .btn-secondary {
    font-family: 'Nunito', sans-serif;
    font-weight: 800;
    font-size: 1.1rem;
    padding: 0.8rem 1.8rem;
    border-radius: 50px;
    border: none;
    cursor: pointer;
    box-shadow: 0 8px 15px var(--shadow-color);
    transition: all 0.3s ease;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-3px) scale(1.05);
    box-shadow: 0 12px 20px var(--shadow-color);
}

.btn-secondary {
    background: var(--secondary-color);
    color: var(--text-color);
    margin-top: 1rem;
}

.btn-secondary:hover {
    filter: brightness(0.95);
    transform: translateY(-2px);
}

/* Hidden elements */
.hidden {
    display: none;
    margin-top: 1rem;
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--primary-color);
    animation: popIn 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}

/* Hero Image & Blob */
.hero-image {
    flex: 1;
    position: relative;
    display: flex;
    justify-content: center;
}

.hero-image img {
    border-radius: 30px;
    width: 100%;
    max-width: 400px;
    object-fit: cover;
    box-shadow: 0 15px 25px var(--shadow-color);
    position: relative;
    z-index: 2;
    border: 4px solid var(--card-bg);
}

.floating {
    animation: float 6s ease-in-out infinite;
}

/* Decorative background blob */
.blob {
    position: absolute;
    width: 350px;
    height: 350px;
    background: var(--secondary-color);
    border-radius: 40% 60% 70% 30% / 40% 50% 60% 50%;
    z-index: 1;
    animation: morph 8s ease-in-out infinite alternate;
}

/* Section Title */
.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin: 3rem 0 2rem;
}

/* Glass Card styling */
.glass-card {
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--card-border);
    border-radius: 25px;
    padding: 2rem;
    box-shadow: 0 10px 30px var(--shadow-color);
}

/* Cards Grid */
.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.cards-grid .glass-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    transition: transform 0.3s ease;
}

.cards-grid .glass-card:hover {
    transform: translateY(-10px);
}

.cards-grid img {
    width: 100%;
    height: 250px;
    object-fit: cover;
    border-radius: 15px;
    margin-bottom: 1.5rem;
}

/* Fun Facts */
.fun-facts {
    margin-top: 4rem;
    text-align: center;
    padding: 3rem 2rem;
}

.fact-box p {
    font-size: 1.3rem;
    font-weight: 600;
    min-height: 3rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Floating Hearts Container */
#heart-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    pointer-events: none;
    z-index: 9999;
}

.heart {
    position: absolute;
    bottom: -100px;
    font-size: 2rem;
    animation: floatUp 3s ease-in-out forwards;
    opacity: 0;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem;
    margin-top: 2rem;
    font-weight: 600;
    opacity: 0.8;
}

/* Calculator Form */
.calc-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    max-width: 500px;
    margin: 0 auto;
}

.input-group {
    display: flex;
    flex-direction: column;
    text-align: left;
}

.input-group label {
    font-weight: 800;
    margin-bottom: 0.5rem;
    color: var(--primary-color);
}

.input-group input, .input-group select {
    font-family: 'Nunito', sans-serif;
    font-size: 1.1rem;
    padding: 0.8rem 1rem;
    border: 2px solid var(--card-border);
    border-radius: 12px;
    background: rgba(255,255,255,0.7);
    color: #333; /* Ensuring contrast on inputs */
    outline: none;
    transition: all var(--transition-speed);
}

[data-theme="dark"] .input-group input, [data-theme="dark"] .input-group select {
    background: rgba(0,0,0,0.3);
    color: var(--text-color);
}

.input-group input:focus, .input-group select:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 10px var(--shadow-color);
}

.result-box {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--card-bg);
    border-radius: 15px;
    border: 1px dashed var(--primary-color);
    text-align: center;
}

.result-box h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

/* Keyframe Animations */
@keyframes float {
    0% { transform: translateY(0px); }
    50% { transform: translateY(-20px); }
    100% { transform: translateY(0px); }
}

@keyframes morph {
    0% { border-radius: 40% 60% 70% 30% / 40% 50% 60% 50%; }
    100% { border-radius: 60% 40% 30% 70% / 60% 30% 70% 40%; }
}

@keyframes wave {
    0%, 100% { transform: rotate(0deg); }
    25% { transform: rotate(15deg); }
    75% { transform: rotate(-15deg); }
}

@keyframes popIn {
    0% { transform: scale(0); opacity: 0; }
    100% { transform: scale(1); opacity: 1; }
}

@keyframes floatUp {
    0% {
        transform: translateY(0) scale(0.5);
        opacity: 1;
    }
    100% {
        transform: translateY(-80vh) scale(1.5) rotate(20deg);
        opacity: 0;
    }
}

/* Didactic Explanation Box */
.explanation-box {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background: rgba(255, 255, 255, 0.6);
    border-radius: 12px;
    border-left: 5px solid var(--primary-color);
    text-align: left;
    font-size: 0.95rem;
    color: var(--text-color);
}

[data-theme="dark"] .explanation-box {
    background: rgba(0, 0, 0, 0.4);
}

.explanation-box h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-family: 'Nunito', sans-serif;
}

.explanation-box ul {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

.explanation-box code {
    background: rgba(0,0,0,0.1);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-family: monospace;
    font-size: 1.05rem;
    color: var(--primary-hover);
}

[data-theme="dark"] .explanation-box code {
    background: rgba(255,255,255,0.1);
    color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero {
        flex-direction: column;
        text-align: center;
    }
    .title-primary {
        font-size: 2.5rem;
    }
    .hero-image img {
        max-width: 300px;
    }
    .blob {
        width: 250px;
        height: 250px;
    }
}