/* ========================================================
   SmartCalc Modern CSS Stylesheet
   Compatible with PHP & MySQL Application
   ======================================================== */

:root {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --header-bg: #0f172a;
    --border-color: #334155;
    
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    
    --primary: #3b82f6;
    --primary-hover: #2563eb;
    --primary-light: rgba(59, 130, 246, 0.15);
    
    --danger: #ef4444;
    --danger-hover: #dc2626;
    
    --key-num-bg: #334155;
    --key-num-hover: #475569;
    --key-num-text: #f8fafc;
    
    --key-op-bg: #2563eb;
    --key-op-hover: #1d4ed8;
    --key-op-text: #ffffff;
    
    --key-op-alt-bg: #475569;
    --key-op-alt-hover: #64748b;
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
    
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
}

/* Light Theme Override Variables */
body.light-theme {
    --bg-color: #f1f5f9;
    --card-bg: #ffffff;
    --header-bg: #ffffff;
    --border-color: #cbd5e1;
    
    --text-main: #0f172a;
    --text-muted: #64748b;
    
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: rgba(37, 99, 235, 0.1);
    
    --key-num-bg: #f8fafc;
    --key-num-hover: #e2e8f0;
    --key-num-text: #0f172a;
    
    --key-op-bg: #2563eb;
    --key-op-hover: #1d4ed8;
    --key-op-text: #ffffff;
    
    --key-op-alt-bg: #e2e8f0;
    --key-op-alt-hover: #cbd5e1;
    
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg-color);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background-color 0.3s ease, color 0.3s ease;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.2s;
}

a:hover {
    color: var(--primary-hover);
}

/* ================= Top Header ================= */
.app-header {
    background-color: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 16px 24px;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.header-container {
    max-width: 1100px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
}

.brand-icon {
    font-size: 1.8rem;
}

.brand h1 {
    font-size: 1.4rem;
    font-weight: 400;
    letter-spacing: -0.5px;
}

.brand h1 strong {
    font-weight: 700;
    color: var(--primary);
}

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

.theme-toggle-btn {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-main);
    padding: 6px 14px;
    border-radius: var(--radius-lg);
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: all 0.2s ease;
}

.theme-toggle-btn:hover {
    border-color: var(--primary);
    transform: scale(1.05);
}

body.light-theme .theme-icon-light {
    display: none;
}
body.light-theme .theme-icon-dark {
    display: inline;
}
body:not(.light-theme) .theme-icon-light {
    display: inline;
}
body:not(.light-theme) .theme-icon-dark {
    display: none;
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--card-bg);
    padding: 6px 14px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.avatar {
    width: 28px;
    height: 28px;
    background: var(--primary);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.85rem;
}

.username {
    font-weight: 600;
    font-size: 0.95rem;
}

/* ================= Centered Main Layout ================= */
.main-layout {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 32px 16px;
}

.layout-container {
    max-width: 900px;
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 32px;
    margin: 0 auto;
}

/* ================= Calculator Card (Centered) ================= */
.calculator-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    gap: 20px;
    width: 100%;
    max-width: 380px;
    margin: 0 auto;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.calculator-display-wrapper {
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
    text-align: right;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    min-height: 100px;
    word-wrap: break-word;
    word-break: break-all;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.calculator-expression {
    font-family: var(--font-mono);
    font-size: 0.95rem;
    color: var(--text-muted);
    min-height: 22px;
}

.calculator-display {
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-main);
    font-family: var(--font-mono);
    font-size: 2rem;
    font-weight: 600;
    text-align: right;
    width: 100%;
}

.calculator-keypad {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

.btn-key {
    height: 58px;
    border-radius: var(--radius-md);
    border: none;
    font-family: var(--font-mono);
    font-size: 1.25rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s ease;
    user-select: none;
}

.btn-key:active {
    transform: scale(0.95);
}

.btn-num {
    background-color: var(--key-num-bg);
    color: var(--key-num-text);
}

.btn-num:hover {
    background-color: var(--key-num-hover);
}

.btn-operator {
    background-color: var(--key-op-bg);
    color: var(--key-op-text);
}

.btn-operator:hover {
    background-color: var(--key-op-hover);
}

.btn-operator-alt {
    background-color: var(--key-op-alt-bg);
    color: var(--text-main);
}

.btn-operator-alt:hover {
    background-color: var(--key-op-alt-hover);
}

.btn-equals {
    grid-column: span 4;
    background-color: var(--primary);
    color: #ffffff;
    font-size: 1.5rem;
    height: 52px;
}

.btn-equals:hover {
    background-color: var(--primary-hover);
}

/* ================= History Drawer Card (Centered) ================= */
.history-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow);
    min-height: 380px;
    max-height: 480px;
    display: flex;
    flex-direction: column;
    width: 100%;
    max-width: 520px;
    margin: 0 auto;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.history-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 16px;
}

.history-header h2 {
    font-size: 1.2rem;
    font-weight: 600;
}

.history-list {
    flex: 1;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-right: 4px;
}

.history-list::-webkit-scrollbar {
    width: 6px;
}
.history-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.history-item {
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 12px 16px;
    cursor: pointer;
    transition: transform 0.15s, border-color 0.15s, background-color 0.3s;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.history-item:hover {
    border-color: var(--primary);
    transform: translateX(3px);
}

.history-expr {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--text-muted);
}

.history-res {
    font-family: var(--font-mono);
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary);
}

.history-date {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-align: right;
}

.history-empty {
    color: var(--text-muted);
    text-align: center;
    margin: auto 0;
    font-style: italic;
}

/* ================= Guest History Notice ================= */
.history-guest-notice {
    text-align: center;
    margin: auto 0;
    padding: 24px 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.notice-icon {
    font-size: 3rem;
}

.history-guest-notice h3 {
    font-size: 1.3rem;
}

.history-guest-notice p {
    color: var(--text-muted);
    font-size: 0.95rem;
    max-width: 320px;
    line-height: 1.5;
}

.notice-actions {
    display: flex;
    gap: 12px;
    width: 100%;
    max-width: 280px;
    margin-top: 8px;
}

/* ================= Buttons & Form Utilities ================= */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 18px;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s, border-color 0.2s, color 0.2s;
    border: none;
}

.btn-primary {
    background-color: var(--primary);
    color: #ffffff;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
}

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

.btn-outline:hover {
    border-color: var(--primary);
    color: var(--primary);
}

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

.btn-outline-danger:hover {
    background-color: var(--danger);
    color: #ffffff;
    border-color: var(--danger);
}

.btn-sm {
    padding: 4px 10px;
    font-size: 0.85rem;
}

.btn-link-danger {
    background: transparent;
    border: none;
    color: var(--danger);
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 500;
}

.btn-link-danger:hover {
    text-decoration: underline;
}

.btn-block {
    width: 100%;
}

/* ================= Authentication Pages ================= */
.auth-page {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.auth-container {
    width: 100%;
    max-width: 420px;
}

.auth-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow);
}

.auth-header {
    margin-bottom: 24px;
}

.back-link {
    font-size: 0.85rem;
    display: inline-block;
    margin-bottom: 12px;
}

.auth-header h2 {
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 6px;
}

.auth-header p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.form-group label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
}

.form-group input {
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 12px 14px;
    color: var(--text-main);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    outline: none;
    transition: border-color 0.2s;
}

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

.auth-footer {
    margin-top: 24px;
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-muted);
}

.alert {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    margin-bottom: 16px;
}

.alert-danger {
    background-color: rgba(239, 68, 68, 0.15);
    border: 1px solid var(--danger);
    color: #fca5a5;
}

.alert-success {
    background-color: rgba(34, 197, 94, 0.15);
    border: 1px solid #22c55e;
    color: #86efac;
}

/* ================= Footer ================= */
.app-footer {
    text-align: center;
    padding: 20px;
    font-size: 0.85rem;
    color: var(--text-muted);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}