:root {
    --bg-body: #0b0f19;
    --primary: #4f46e5;
    --primary-gradient: linear-gradient(135deg, #4f46e5 0%, #8b5cf6 100%);
    --secondary-gradient: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
    --glass-surface: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.08);
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --success: #10b981;
    --error: #ef4444;
    --radius-lg: 24px;
    --radius-md: 16px;
    --radius-sm: 12px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: transparent;
    font-family: 'Plus Jakarta Sans', sans-serif;
}

body {
    background-color: var(--bg-body);
    background-image: 
        radial-gradient(circle at 10% 20%, rgba(79, 70, 229, 0.15) 0%, transparent 40%),
        radial-gradient(circle at 90% 80%, rgba(6, 182, 212, 0.15) 0%, transparent 40%);
    color: var(--text-main);
    min-height: 100vh;
    padding: 20px 20px 100px 20px; /* Padding bawah extra untuk navigasi mobile */
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* --- ICONS (SVG) --- */
.icon {
    width: 20px;
    height: 20px;
    fill: currentColor;
}

/* --- HEADER & BRANDING --- */
header {
    width: 100%;
    max-width: 600px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 25px;
    padding: 10px 0;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-shape {
    width: 42px;
    height: 42px;
    background: var(--primary-gradient);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 0 20px rgba(79, 70, 229, 0.3);
    position: relative;
    overflow: hidden;
}

.logo-shape::after {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: linear-gradient(45deg, transparent 40%, rgba(255,255,255,0.2) 50%, transparent 60%);
}

.brand-info h1 {
    font-size: 1.25rem;
    font-weight: 800;
    letter-spacing: -0.5px;
    line-height: 1.1;
}

.brand-info span {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.developer-badge {
    font-size: 0.7rem;
    background: rgba(255,255,255,0.05);
    padding: 6px 12px;
    border-radius: 20px;
    border: 1px solid var(--glass-border);
    color: #a5b4fc;
}

/* --- MAIN CONTAINER --- */
.container {
    width: 100%;
    max-width: 600px;
    position: relative;
}

.card {
    background: var(--glass-surface);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    padding: 25px;
    box-shadow: 0 10px 30px -10px rgba(0,0,0,0.5);
    animation: fadeIn 0.4s ease-out;
    margin-bottom: 20px;
}

.card-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--glass-border);
}

.card-header h2 {
    font-size: 1.1rem;
    font-weight: 700;
    margin: 0;
}

/* --- NAVIGATION (Mobile Optimized) --- */
.nav-dock {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    width: 90%;
    max-width: 500px;
    background: rgba(15, 23, 42, 0.9);
    backdrop-filter: blur(16px);
    padding: 10px;
    border-radius: 24px;
    display: flex;
    justify-content: space-between;
    border: 1px solid rgba(255,255,255,0.1);
    box-shadow: 0 10px 40px rgba(0,0,0,0.4);
    z-index: 1000;
}

.nav-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    color: var(--text-muted);
    padding: 8px 0;
    cursor: pointer;
    transition: all 0.3s ease;
    gap: 4px;
}

.nav-item svg {
    width: 24px;
    height: 24px;
    stroke: currentColor;
    stroke-width: 2;
    fill: none;
    transition: all 0.3s;
}

.nav-item.active {
    color: #fff;
}

.nav-item.active svg {
    stroke: #818cf8;
    filter: drop-shadow(0 0 8px rgba(129, 140, 248, 0.5));
}

.nav-label {
    font-size: 0.65rem;
    font-weight: 600;
}

/* --- INPUTS & FORMS --- */
input[type="text"], textarea, select, input[type="file"] {
    width: 100%;
    background: rgba(0,0,0,0.2);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-sm);
    padding: 16px;
    color: #fff;
    font-size: 1rem;
    outline: none;
    transition: 0.3s;
}

input:focus, textarea:focus, select:focus {
    border-color: #6366f1;
    background: rgba(0,0,0,0.3);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.2);
}

/* --- BUTTONS --- */
.btn-primary {
    width: 100%;
    padding: 16px;
    border-radius: var(--radius-sm);
    border: none;
    background: var(--primary-gradient);
    color: white;
    font-weight: 700;
    font-size: 1rem;
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(79, 70, 229, 0.3);
    transition: transform 0.2s;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
}

.btn-primary:active { transform: scale(0.98); }
.btn-secondary { background: #334155; color: white; }
.btn-danger { background: #ef4444; color: white; }

/* --- CALCULATOR GRID --- */
.calc-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.calc-btn {
    aspect-ratio: 1;
    background: rgba(255,255,255,0.03);
    border: 1px solid var(--glass-border);
    border-radius: 14px;
    color: white;
    font-size: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: 0.2s;
}

.calc-btn:active { background: rgba(255,255,255,0.1); }
.calc-btn.op { color: #67e8f9; background: rgba(6, 182, 212, 0.1); }
.calc-btn.fn { color: #a5b4fc; font-size: 0.9rem; font-weight: 600; }
.calc-btn.eq { 
    grid-column: span 2; 
    aspect-ratio: auto; 
    background: var(--primary); 
    box-shadow: 0 0 15px rgba(79, 70, 229, 0.4);
    border: none;
}

/* --- OUTPUT AREA --- */
.output-display {
    background: rgba(15, 23, 42, 0.6);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 20px;
    text-align: right;
    word-break: break-all;
    border: 1px solid var(--glass-border);
}

.output-result {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--success);
    margin-top: 5px;
}

/* --- MENU GRID --- */
.menu-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 15px;
}

@media (min-width: 480px) {
    .menu-grid { grid-template-columns: 1fr 1fr; }
}

.menu-item {
    background: rgba(255,255,255,0.02);
    border: 1px solid var(--glass-border);
    padding: 20px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: 15px;
    cursor: pointer;
    transition: 0.3s;
}

.menu-item:hover {
    background: rgba(255,255,255,0.05);
    border-color: var(--primary);
}

.menu-icon-box {
    width: 45px;
    height: 45px;
    border-radius: 12px;
    background: rgba(99, 102, 241, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #818cf8;
}

/* --- UTILS --- */
.hidden { display: none; }
.loading { text-align: center; padding: 20px; color: #67e8f9; font-size: 0.9rem; }
.history-item { padding: 12px; border-bottom: 1px solid var(--glass-border); font-size: 0.9rem; }
.badge-pro { background: var(--secondary-gradient); font-size: 0.6rem; padding: 2px 6px; border-radius: 4px; color: white; vertical-align: middle; margin-left: 5px;}

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

/* Mobile Adjustments */
@media (max-width: 380px) {
    .calc-btn { font-size: 1rem; border-radius: 10px; }
    h1 { font-size: 1.1rem; }
}