:root {
    --bg: #f0f0f0;
    --form-bg: #ffffff;
    --receipt-bg: #fffef0;
    --accent: #2c2c2c;
    --border: #cccccc;
    --label-color: #555555;
    --input-border: #dddddd;
    --btn-add: #3b82f6;
    --btn-print: #16a34a;
    --grand-total-bg: #2c2c2c;
    --grand-total-text: #ffffff;
    --font-receipt: 'Courier New', Courier, monospace;
    --font-form: 'Segoe UI', sans-serif;
}

/*BASE & RESET*/

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

body {
    background-color: var(--bg);
    font-family: var(--font-form);
    min-height: 100vh;
    padding: 30px 20px;
    scroll-behavior: smooth;
}

/*APP LAYOUT - side by side*/

.app {
    display: flex;
    gap: 30px;
    max-width: 1100px;
    margin: 0 auto;
    align-items: flex-start;
}

/*FORM PANEL - left side*/

.form-panel {
    flex: 1;
    background: var(--form-bg);
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.08);
}

.form-panel h2 {
    font-size: 1.4rem;
    margin-bottom: 20px;
    color: var(--accent);
    border-bottom: 2px solid var(--border);
    padding-bottom: 10px;
}

.form-panel h3 {
    font-size: 1rem;
    color: var(--label-color);
    margin-bottom: 10px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.form-panel hr {
    border: none;
    border-top: 1px solid var(--border);
    margin: 20px 0;
}

/*FORM GROUPS - label + input*/

.form-group {
    display: flex;
    flex-direction: column;
    gap: 5px;
    margin-bottom: 14px;
}

.form-group label {
    font-size: 0.82rem;
    color: var(--label-color);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.form-group input, 
.form-group select {
    padding: 9px 12px;
    border: 1px solid var(--input-border);
    border-radius: 6px;
    font-size: 0.95rem;
    font-family: var(--font-form);
    transition: border-color 0.2s;
    outline: none;
}

.form-group select:focus {
    border-color: var(--btn-add);
    outline: none;
}

.form-group input:focus {
    border-color: var(--btn-add);
}

/*ITEM ROW -inside items container*/

.item-row {
    display: flex;
    gap: 8px;
    margin-bottom: 8px;
    align-items: center;
}

.item-row input {
    padding: 8px 10px;
    border: 1px solid var(--input-border);
    border-radius: 6px;
    font-size: 0.9rem;
    outline: none;
}

/* N EACH INPUT GETS A DIFFERENT WIDTH */

.item-row .item-desc { flex: 3; }
.item-row .item-qty { flex: 1; }
.item-row .item-price { flex: 1.5; }

.item-row input:focus {
    border-color: var(--btn-add);
}

/*REMOVE ITEM BUTTON*/

.remove-item-btn {
    background: none;
    border: none;
    color: #e53e3e;
    font-size: 1.2rem;
    cursor: pointer;
    padding: 0 4px;
    line-height: 1;
}

.remove-item-btn:hover {
    color: #c53030;
}

/*BUTTONS*/

#add-item-btn {
    background: var(--btn-add);
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 6px;
    font-size: 0.9rem;
    cursor: pointer;
    margin-bottom: 4px;
    transition: background 0.2s;
}

#add-item-btn:hover {
    background: #2563eb;
}

#print-btn {
    width: 100%;
    background: var(--btn-print);
    color: white;
    border: none;
    padding: 12px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 10px;
    transition: background 0.2s;
}

/*CLEAR BUTTON*/

#clear-btn {
    width: 100%;
    background: white;
    color: #e53e3e;
    border: 2px solid #e53e3e;
    padding: 10px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 8px;
    transition: all 0.2s;
}

#clear-btn:hover {
    background: #e53e3e;
    color: white;
}

#print-btn:hover {
    background: #15803d;
}

/*NEXT INVOICE*/

#next-invoice-btn {
    width: 100%;
    background: white;
    color: #7c3aed;
    border: 2px solid #7c3aed;
    padding:  8px;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 6px;
    transition: all 0.2s;
}

#next-invoice-btn:hover {
    background: #7c3aed;
    color: white;
}

/*RECIEPT PANEL -right side */

.receipt-panel {
    flex: 0 0 380px;
    position: sticky;
    top: 30px;
}
/*THIS IS THE RECIEPT ITSELF*/

.receipt {
    background: var(--receipt-bg);
    font-family: var(--font-receipt);
    padding: 30px 28px;
    border-radius: 4px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.12),
    0 1px 4px rgba(0,0,0,0.08);
    position: relative; /*PAID STAMP*/

    /*JAGGED BOTTOM EDGE -torn reciept effect*/

    -webkit-mask-image:
    linear-gradient(white, white),
    radial-gradient(circle at 50% 0, transparent 8px, white 8px);
    -webkit-mask-size: 100% calc(100% - 12px), 20px 12px;
    -webkit-mask-position: top, bottom;
    -webkit-mask-repeat: no-repeat, repeat-x;
}

/*RECIEPT HEADER*/

.receipt-header  {
    text-align: center;
    margin-bottom: 6px;
}

.paid-stamp {
    display: none; /*HIDDEN BY DEFAULT*/
    position: absolute; /*FLOATS OVER THE RECEIPT*/
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) rotate(-30deg);
    font-size: 3.5rem;
    font-weight: 900;
    color: rgba(22, 163, 74, 0.85);
    border: 6px solid rgba(22, 163, 74, 0.85);
    border-radius: 8px;
    padding: 6px 18px;
    letter-spacing: 8px;
    pointer-events: none; /*STAMP WON'T BLOCK CLICKS ON RECEIPT.....*/
    z-index: 10;
    font-family: var(--font-receipt);
    text-transform: uppercase;
}

/*N WHEN .paid CLASS IS ON THE RECEIPT, SHOW THE STAMP*/

.receipt.paid .paid-stamp {
    display: block;
}

/*PAID BUTTON STYLES*/
#paid-btn {
    width: 100%;
    background: white;
    color: #16a34a;
    border: 2px solid #16a34a;
    padding: 10px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 10px;
    transition: all 0.2s;
}

#paid-btn:hover {
    background: #16a34a;
    color: white;
}

/*WHEN PAID - BUTTON TURNS RED TO ALLOW UNDOING*/

#paid-btn.active {
    background: #dc2626;
    border-color: #dc2626;
    color: white;
}

#paid-btn.active:hover {
    background: #b91c1c;
    border-color: #b91c1c;
}

 /*LOGO*/
 
#r-logo {
    width: 80px;
    height: 80px;
    object-fit: contain;  /*KEEPS PROPORTIONS, NO STRETCHING*/
    margin-bottom: 8px;
    display: none; 
}

.receipt-header h1 {
    font-size: 1.3rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--accent);
}

.receipt-header p {
    font-size: 0.8rem;
    color: #666;
    margin-top: 4px;
}

/*DASHED DIVIDER -the reciept look*/

.divider {
    border: none;
    border-top: 2px dashed var(--border);
    margin: 12px 0;
}

/*META INFO (invoice number, date, client*/

.receipt-meta .meta-row {
    display: flex;
    justify-content: space-between;
    font-size: 0.82rem;
    margin-bottom: 5px;
    color: var(--accent);
}

/*ITEMS HEADER (item | qty | price | total)*/

.items-header {
    display: grid;
    grid-template-columns: 3fr 1fr 1.5fr 1.5fr;
    font-size: 0.75rem;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: #888;
    margin-bottom: 6px;
}

/*EACH ITEM ROW ON RECIEPT*/

.r-item-row {
    display: grid;
    grid-template-columns: 3fr 1fr 1.5fr 1.5fr;
    font-size: 0.85rem;
    padding: 4px 0;
    color: var(--accent);
    border-bottom: 1px dotted var(--border);
}

/*TOTALS SECTION*/
.totals .total-row {
    display: flex;
    justify-content: space-between;
    font-size: 0.88rem;
    padding: 4px 0;
    color: var(--accent);
}

/*GRAND TOTAL ROW -bold and higlighted*/

.totals .grand-total {
    background: var(--grand-total-bg);
    color: var(--grand-total-text);
    padding: 8px 10px;
    border-radius: 4px;
    font-size: 1rem;
    font-weight: bold;
    letter-spacing: 1px;
    margin-top: 6px;
}

/*RECIEPT FOOTER*/

.receipt-footer {
    text-align: center;
    font-size: 0.82rem;
    color: #777;
    padding-top: 4px;
}

/*PRINT STYLES -hides the form*/

@media print {
    body {
        background: white;
        padding: 0;
    }

    .form-panel {
        display: none;
    }

    .receipt-panel {
        position: static;
        width: 100%;
    }

    .receipt {
        box-shadow: none;
        width: 100%;
        max-width: 400px;
        margin: 0 auto;
    }

}

/*RESPONSIVE -stack on small screens*/

@media (max-width: 750px) {
    .app {
        flex-direction: column;
    }

    .receipt-panel {
        flex: 1;
        width: 100%;
        position: static;
    }
}