@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

:root {
    --bg-dark: #0f172a;
    --bg-card: rgba(30, 41, 59, 0.7);
    --border-light: rgba(255, 255, 255, 0.1);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-blue: #3b82f6;
    --accent-purple: #8b5cf6;
    --accent-success: #10b981;
    --accent-danger: #ef4444;
}

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

body {
    font-family: 'Inter', sans-serif;
    background: radial-gradient(circle at 10% 20%, rgb(18, 24, 43) 0%, rgb(15, 23, 42) 90%);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow-x: hidden;
}

/* Glass Header */
header {
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-light);
    padding: 20px 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

header h1 {
    font-size: 2.2rem;
    font-weight: 700;
    text-align: center;
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    padding-bottom: 15px;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    gap: 15px;
    flex-wrap: wrap;
    padding: 0 20px;
}

nav ul li a, .back-to-home {
    display: inline-block;
    padding: 10px 20px;
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-light);
    transition: all 0.3s ease;
}

nav ul li a:hover, .back-to-home:hover, nav ul li a.active {
    background: rgba(255, 255, 255, 0.15);
    border-color: var(--accent-blue);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.2);
}

.back-to-home {
    margin: 0 auto;
    display: block;
    width: max-content;
}

/* Main Layout */
main {
    flex: 1;
    width: 100%;
    max-width: 1200px;
    margin: 40px auto;
    padding: 0 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

main > p {
    color: var(--text-secondary);
    font-size: 1.1rem;
    text-align: center;
    max-width: 800px;
    margin-bottom: 30px;
}

/* Glass Cards */
.card, .slider-container, .input-container, .controls, .lechateliers-container {
    background: var(--bg-card);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    padding: 25px;
    width: 100%;
    max-width: 800px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    margin-bottom: 30px;
}

.input-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

label {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-primary);
}

/* Form Controls */
input[type="number"], input[type="text"], select {
    width: 100%;
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--border-light);
    color: var(--text-primary);
    padding: 12px;
    border-radius: 8px;
    font-size: 1rem;
    font-family: 'Inter', sans-serif;
    transition: all 0.3s ease;
}

input[type="number"]:focus, input[type="text"]:focus, select:focus {
    outline: none;
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

/* Custom Range Slider */
input[type="range"] {
    -webkit-appearance: none;
    width: 100%;
    height: 8px;
    background: rgba(255, 255, 255, 0.1);
    outline: none;
    border-radius: 4px;
    margin-top: 10px;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--accent-blue);
    cursor: pointer;
    box-shadow: 0 0 10px var(--accent-blue);
    transition: transform 0.2s;
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.2);
}

/* Buttons */
button {
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    color: white;
    border: none;
    padding: 12px 24px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.5);
}

button:active {
    transform: translateY(1px);
}

.button-container, .button {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-top: 20px;
    width: 100%;
}

/* Canvas & Charts */
canvas {
    background: var(--bg-card);
    border-radius: 12px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
    border: 1px solid var(--border-light);
}

#chartCanvas {
    width: 100% !important;
    max-width: 800px;
    height: 400px !important;
}

#visualization {
    width: 100% !important;
    max-width: 800px;
    height: 400px !important;
    margin-bottom: 20px;
}

#chart, .chart-container {
    width: 100%;
    max-width: 800px;
    position: relative;
    background: var(--bg-card);
    border-radius: 12px;
    padding: 15px;
    border: 1px solid var(--border-light);
}

/* Value Displays */
span[id$="-value"], #k-value, #calculated-kc, #kc-formula {
    color: var(--accent-success);
    font-weight: 700;
    font-size: 1.1rem;
}

#result, #lechateliers-output {
    margin-top: 20px;
    padding: 20px;
    background: rgba(16, 185, 129, 0.1);
    border: 1px solid rgba(16, 185, 129, 0.2);
    border-radius: 8px;
    color: var(--accent-success);
    font-weight: 600;
    font-size: 1.2rem;
    text-align: center;
}

/* Footer */
footer {
    background: rgba(15, 23, 42, 0.9);
    border-top: 1px solid var(--border-light);
    color: var(--text-secondary);
    text-align: center;
    padding: 20px;
    margin-top: 40px;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

main > * {
    animation: fadeIn 0.5s ease forwards;
}

/* Layout Utilities for dual charts */
.dual-chart-container {
    display: flex;
    flex-direction: row;
    gap: 20px;
    width: 100%;
    max-width: 1200px;
}

.dual-chart-container .chart-wrapper {
    flex: 1;
    min-width: 0; 
}

/* Responsive */
@media (max-width: 850px) {
    .dual-chart-container {
        flex-direction: column;
    }
    
    header h1 {
        font-size: 1.8rem;
    }
    
    nav ul {
        flex-direction: column;
        align-items: center;
    }
    
    .input-container {
        grid-template-columns: 1fr;
    }
}