:root {
    --bg-slate: #020617;
    --card-bg: rgba(15, 23, 42, 0.65);
    --primary: #38bdf8;
    --secondary: #818cf8;
    --accent: #c084fc;
    --success: #34d399;
    --warning: #fbbf24;
    --error: #f87171;
    --text-main: #f1f5f9;
    --text-muted: #94a3b8;
    --border-subtle: rgba(255, 255, 255, 0.08);
    --glass-border: rgba(255, 255, 255, 0.12);
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --glow: 0 0 20px rgba(56, 189, 248, 0.15);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    background-color: var(--bg-slate);
    background-image: 
        radial-gradient(at 0% 0%, rgba(56, 189, 248, 0.08) 0, transparent 50%),
        radial-gradient(at 100% 100%, rgba(129, 140, 248, 0.08) 0, transparent 50%);
    color: var(--text-main);
    font-family: var(--font-sans);
    line-height: 1.5;
    min-height: 100vh;
    overflow-x: hidden;
}

/* --- Hero Section Styles --- */
.hero-container {
    position: relative;
    height: 60vh;
    width: 100%;
    background: url('assets/hero-bg.jpg') center/cover no-repeat;
    display: flex;
    align-items: center;
    justify-content: center;
}

.hero-overlay {
    position: absolute;
    inset: 0;
    background: linear-gradient(to bottom, rgba(2, 6, 23, 0.4), var(--bg-slate));
}

/* --- Premium Glassmorphism --- */
.glass-card {
    position: relative;
    background: var(--card-bg);
    backdrop-filter: blur(16px) saturate(180%);
    -webkit-backdrop-filter: blur(16px) saturate(180%);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1.5rem;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    overflow: hidden;
}

.glass-card::before {
    content: '';
    position: absolute;
    top: 0; left: -100%;
    width: 100%; height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.03), transparent);
    transition: 0.5s;
}

.glass-card:hover::before {
    left: 100%;
}

.glass-card:hover {
    transform: translateY(-4px);
    border-color: rgba(56, 189, 248, 0.3);
    box-shadow: var(--glow);
}

.gradient-text {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 50%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-weight: 800;
    letter-spacing: -0.02em;
}

/* --- Engineering Inputs (Mobile First) --- */
.input-group {
    margin-bottom: 1.5rem;
}

.input-group label {
    display: block;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.input-field {
    width: 100%;
    background: rgba(2, 6, 23, 0.8);
    border: 1px solid var(--glass-border);
    border-radius: 0.5rem;
    padding: 0.875rem 1rem;
    color: var(--primary);
    font-family: var(--font-mono);
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.input-field:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(56, 189, 248, 0.1);
}

.btn-calculate {
    width: 100%;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: #fff;
    border: none;
    padding: 1rem;
    border-radius: 0.5rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    cursor: pointer;
    transition: filter 0.2s, transform 0.1s;
}

.btn-calculate:active {
    transform: scale(0.98);
}

.btn-calculate:hover {
    filter: brightness(1.1);
}

/* --- Result & Status Display --- */
.result-display {
    margin-top: 2rem;
    padding: 1.5rem;
    background: rgba(52, 211, 153, 0.03);
    border-left: 4px solid var(--success);
    border-radius: 0 0.5rem 0.5rem 0;
}

.result-value {
    font-family: var(--font-mono);
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--success);
    line-height: 1;
}

/* --- Data Architecture --- */
.data-table-container {
    overflow-x: auto;
    width: 100%;
}

.data-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin-top: 1rem;
}

.data-table th {
    text-align: left;
    padding: 1rem;
    background: rgba(255, 255, 255, 0.02);
    color: var(--text-muted);
    font-size: 0.75rem;
    text-transform: uppercase;
    border-bottom: 1px solid var(--glass-border);
}

.data-table td {
    padding: 1rem;
    border-bottom: 1px solid var(--border-subtle);
    font-size: 0.875rem;
}

/* --- Responsive Layout Engine --- */
.tool-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
    padding: 1.5rem;
    max-width: 1400px;
    margin: 0 auto;
}

@media (min-width: 768px) {
    .tool-grid {
        grid-template-columns: repeat(2, 1fr);
        padding: 3rem;
    }
    
    .tool-grid-wide {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (min-width: 1024px) {
    .tool-grid {
        gap: 2.5rem;
    }
}

/* --- HVAC Utility Classes --- */
.animate-airflow {
    animation: airflow-sweep 4s linear infinite;
}

@keyframes airflow-sweep {
    0% { transform: translateX(-5px) skewX(0); opacity: 0.5; }
    50% { transform: translateX(5px) skewX(5deg); opacity: 1; }
    100% { transform: translateX(-5px) skewX(0); opacity: 0.5; }
}

::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-slate);
}

::-webkit-scrollbar-thumb {
    background: var(--glass-border);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}