:root {
    --primary-color: #2563EB; /* Deep Blue */
    --primary-hover: #1D4ED8;
    --primary-light: #EFF6FF;
    --secondary-color: #64748B;
    --secondary-hover: #475569;
    --secondary-light: #F1F5F9;
    --danger-color: #EF4444;
    --danger-hover: #DC2626;
    --success-color: #10B981;
    --background-color: #F8FAFC; /* Soft light background */
    --card-bg: #FFFFFF;
    --text-main: #1E293B;
    --text-muted: #64748B;
    --border-color: #E2E8F0;
    --input-bg: #F8FAFC;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 18px; /* Rounded corners as requested */
}

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

body {
    background-color: var(--background-color);
    color: var(--text-main);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Header */
.header {
    background-color: var(--card-bg);
    padding: 1.25rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav ul {
    list-style: none;
    display: flex;
    gap: 2.5rem;
}

.nav a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    transition: color 0.2s ease;
}

.nav a:hover, .nav a.active {
    color: var(--primary-color);
}

.header-contact {
    display: flex;
    gap: 1.5rem;
}

.contact-link {
    text-decoration: none;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    transition: color 0.2s ease;
}

.contact-link:hover {
    color: var(--primary-color);
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 3rem 1rem;
}

.calculator-container {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 2.5rem;
    max-width: 800px;
    width: 100%;
}

.calculator-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.calculator-header h2 {
    font-size: 1.75rem;
    color: var(--text-main);
    font-weight: 700;
}

/* Size Selector Toggle */
.size-selector {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.selector-label {
    font-weight: 600;
    color: var(--text-muted);
    font-size: 0.95rem;
}

.radio-group {
    display: flex;
    background-color: var(--secondary-light);
    border-radius: var(--radius-sm);
    padding: 0.25rem;
}

.radio-group input[type="radio"] {
    display: none;
}

.radio-group label {
    padding: 0.5rem 1.25rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-muted);
    transition: all 0.2s ease;
}

.radio-group input[type="radio"]:checked + label {
    background-color: white;
    color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

/* Matrices Container */
.matrices-wrapper {
    display: flex;
    gap: 2.5rem;
    margin-bottom: 2.5rem;
    justify-content: center;
    flex-wrap: wrap;
}

.matrix-card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
    flex: 1;
    min-width: 250px;
    max-width: 350px;
    transition: box-shadow 0.3s ease, border-color 0.3s ease;
}

.matrix-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.matrix-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.matrix-header h3 {
    font-size: 1.1rem;
    color: var(--text-main);
}

.icon-btn-small {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    transition: color 0.2s ease;
    font-size: 1rem;
}
.icon-btn-small:hover {
    color: var(--danger-color);
}

/* Matrix Grid Design */
.matrix-grid-container {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.bracket {
    width: 15px;
    height: 100%;
    min-height: 120px;
    border: 2px solid var(--text-main);
    border-radius: 4px;
    transition: all 0.3s ease;
}
.left-bracket {
    border-right: none;
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
}
.right-bracket {
    border-left: none;
    border-top-left-radius: 0;
    border-bottom-left-radius: 0;
}

.matrix-grid {
    display: grid;
    gap: 0.5rem;
    transition: all 0.3s ease;
}

.grid-2x2 { grid-template-columns: repeat(2, 1fr); }
.grid-3x3 { grid-template-columns: repeat(3, 1fr); }

.matrix-input {
    width: 60px;
    height: 50px;
    text-align: center;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-main);
    background-color: var(--input-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    outline: none;
    transition: all 0.2s ease;
    /* Hide arrows */
    -moz-appearance: textfield;
}

.matrix-input::-webkit-outer-spin-button,
.matrix-input::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

.matrix-input:focus {
    border-color: var(--primary-color);
    background-color: white;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Operations Panel */
.operations-panel {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    margin-bottom: 2rem;
}

.op-group {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
}

.btn {
    padding: 0.75rem 1.25rem;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: all 0.2s ease;
}

.btn:active {
    transform: scale(0.97);
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    flex: 1;
    min-width: 140px;
}
.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-secondary {
    background-color: var(--secondary-light);
    color: var(--text-main);
}
.btn-secondary:hover {
    background-color: #E2E8F0;
}

.btn-outline {
    background-color: transparent;
    color: var(--secondary-color);
    border: 1px solid var(--border-color);
}
.btn-outline:hover {
    background-color: var(--secondary-light);
    color: var(--text-main);
}

.btn-danger-outline {
    background-color: transparent;
    color: var(--danger-color);
    border: 1px solid var(--danger-color);
}
.btn-danger-outline:hover {
    background-color: var(--danger-color);
    color: white;
}

.btn-icon {
    background-color: transparent;
    color: var(--text-muted);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
}
.btn-icon:hover {
    background-color: var(--primary-light);
    color: var(--primary-color);
    border-color: var(--primary-color);
}

/* Result Section */
.result-section {
    background-color: var(--card-bg);
    border: 1px solid var(--primary-light);
    border-radius: var(--radius-md);
    padding: 2rem;
    box-shadow: var(--shadow-md);
    animation: slideUpFade 0.4s ease forwards;
    margin-top: 1rem;
}

.result-section.hidden {
    display: none;
}

.result-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

.result-header h3 {
    font-size: 1.25rem;
    color: var(--text-main);
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.badge {
    background-color: var(--primary-light);
    color: var(--primary-color);
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.85rem;
    font-weight: 700;
}

.result-actions {
    display: flex;
    gap: 0.5rem;
}

.result-display-area {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 150px;
    background-color: white;
    padding: 1rem;
    border-radius: var(--radius-sm);
}

.result-content {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-align: center;
}

/* Readonly Result Matrix Cells */
.result-matrix-cell {
    width: 60px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-main);
}

/* Animations */
@keyframes slideUpFade {
    from { opacity: 0; transform: translateY(15px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes flashHighlight {
    0% { background-color: white; }
    50% { background-color: var(--primary-light); }
    100% { background-color: white; }
}
.highlight-anim {
    animation: flashHighlight 0.6s ease;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background-color: var(--text-main);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    transition: all 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    transform: translateY(150%);
    opacity: 0;
}
.toast.show {
    transform: translateY(0);
    opacity: 1;
}
.toast.danger i { color: var(--danger-color); }
.toast.success i { color: var(--success-color); }

/* Footer */
.footer {
    background-color: var(--card-bg);
    padding: 2rem;
    text-align: center;
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: auto;
}
.text-danger { color: var(--danger-color); }
.footer-contact {
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 0.95rem;
}
.footer-contact a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.2s ease;
}
.footer-contact a:hover {
    color: var(--primary-color);
}