:root {
    --bg-color: #f8fafc;
    --container-bg: #ffffff;
    --primary-color: #6366f1; /* Modern Indigo */
    --primary-hover: #4f46e5;
    --text-main: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --accent-color: #10b981; /* Emerald */
    --danger-color: #ef4444;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 10px 25px -5px rgba(0,0,0,0.05), 0 8px 10px -6px rgba(0,0,0,0.05);
    --radius: 12px;
}

* { box-sizing: border-box; margin: 0; padding: 0; font-family: 'Inter', system-ui, sans-serif; }

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    display: flex;
    justify-content: center;
    padding: 40px 20px;
    line-height: 1.5;
}

#container {
    background: var(--container-bg);
    width: 100%;
    max-width: 950px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    border: 1px solid var(--border-color);
}

header {
    padding: 40px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: linear-gradient(to right, #ffffff, #fcfdff);
    border-bottom: 1px solid var(--border-color);
}

#invoice_logo {
    font-size: 24px;
    font-weight: 800;
    color: var(--primary-color);
    letter-spacing: -0.5px;
}

#main_container { padding: 40px; }

#invoice_summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 25px;
    margin-bottom: 40px;
}

.summary label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    margin-bottom: 8px;
}

input, select {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.2s;
    background: #f9fbff;
}

input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
    background: #fff;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

th {
    text-align: left;
    padding: 12px;
    font-size: 12px;
    color: var(--text-secondary);
    border-bottom: 2px solid var(--border-color);
}

td { padding: 12px 8px; border-bottom: 1px solid #f1f5f9; }

.item_total { font-weight: 700; color: var(--text-main); }

.remove_item {
    background: none; border: none; color: #cbd5e1;
    cursor: pointer; font-size: 18px; transition: 0.2s;
}

.remove_item:hover { color: var(--danger-color); transform: scale(1.2); }

#add_item {
    width: 100%;
    margin-top: 20px;
    padding: 12px;
    background: #fff;
    border: 2px dashed var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    color: var(--primary-color);
    font-weight: 600;
}

#add_item:hover { background: #f5f7ff; border-color: var(--primary-color); }

#payment_summary {
    display: flex;
    justify-content: flex-end;
    margin-top: 40px;
    padding-top: 20px;
    border-top: 2px solid var(--border-color);
}

.total_box { text-align: right; }
.total_box p { color: var(--text-secondary); font-size: 14px; }
#total { font-size: 36px; color: var(--primary-color); font-weight: 800; transition: 0.3s; }

#buttons {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 12px;
    margin-top: 40px;
}

button {
    padding: 12px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    background: #fff;
    cursor: pointer;
    font-weight: 600;
    transition: 0.2s;
}

.btn_primary { background: var(--primary-color) !important; color: white !important; border: none !important; }
.btn_primary:hover { background: var(--primary-hover) !important; transform: translateY(-1px); }

#watermark { text-align: center; margin-top: 40px; font-size: 12px; color: var(--text-secondary); }

/* Print Logic */
@media print {
    body { padding: 0; background: white; }
    #container { box-shadow: none; border: none; }
    #buttons, #add_item, .remove_item, #logo_upload { display: none !important; }
    input { border: none !important; background: transparent !important; padding: 0 !important; }
}