/* ========================================
   BaseCalc2 — Innovation University
   Matte Purple Theme + Glassmorphism
   Fully Responsive Design
   ======================================== */

/* ── CSS Custom Properties ── */
:root {
    /* Matte Purple Palette */
    --bg-primary: #2D1B69;
    --bg-secondary: #3D2E7C;
    --bg-tertiary: #4A3B8F;
    --surface: rgba(255, 255, 255, 0.06);
    --surface-hover: rgba(255, 255, 255, 0.10);
    --surface-active: rgba(255, 255, 255, 0.14);
    --glass-bg: rgba(255, 255, 255, 0.08);
    --glass-border: rgba(255, 255, 255, 0.12);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);

    /* Accent Colors */
    --accent-primary: #B794F6;
    --accent-secondary: #9B7DFF;
    --accent-glow: rgba(183, 148, 246, 0.3);
    --accent-gradient: linear-gradient(135deg, #9B7DFF, #B794F6, #D4BBFF);

    /* Text */
    --text-primary: #FFFFFF;
    --text-secondary: rgba(255, 255, 255, 0.75);
    --text-tertiary: rgba(255, 255, 255, 0.5);
    --text-muted: rgba(255, 255, 255, 0.35);

    /* Result Badges */
    --bin-color: #FF6B9D;
    --oct-color: #FFA94D;
    --dec-color: #69DB7C;
    --hex-color: #74C0FC;

    /* Borders & Misc */
    --border-radius: 16px;
    --border-radius-sm: 10px;
    --border-radius-xs: 6px;
    --transition-speed: 0.3s;
    --font-main: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;

    /* Error */
    --error-color: #FF6B6B;
    --error-bg: rgba(255, 107, 107, 0.12);
}

/* Light Theme */
body.light-theme {
    --bg-primary: #E8E0F5;
    --bg-secondary: #D8CCF0;
    --bg-tertiary: #C8B8E8;
    --surface: rgba(255, 255, 255, 0.6);
    --surface-hover: rgba(255, 255, 255, 0.75);
    --surface-active: rgba(255, 255, 255, 0.85);
    --glass-bg: rgba(255, 255, 255, 0.55);
    --glass-border: rgba(255, 255, 255, 0.7);
    --glass-shadow: 0 8px 32px rgba(100, 60, 180, 0.12);
    --accent-primary: #7C4DFF;
    --accent-secondary: #6A3DE8;
    --accent-glow: rgba(124, 77, 255, 0.2);
    --text-primary: #2D1B69;
    --text-secondary: rgba(45, 27, 105, 0.75);
    --text-tertiary: rgba(45, 27, 105, 0.5);
    --text-muted: rgba(45, 27, 105, 0.35);
    --error-bg: rgba(255, 107, 107, 0.15);
}

/* ── Reset & Base ── */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font-main);
    background: linear-gradient(160deg, var(--bg-primary) 0%, var(--bg-secondary) 40%, var(--bg-tertiary) 100%);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    transition: background var(--transition-speed) ease, color var(--transition-speed) ease;
}

.mono {
    font-family: var(--font-mono);
}

/* ── Loading Screen ── */
.loading-screen {
    position: fixed;
    inset: 0;
    z-index: 9999;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(160deg, #2D1B69 0%, #3D2E7C 40%, #4A3B8F 100%);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.loading-screen.fade-out {
    opacity: 0;
    transform: scale(1.05);
    pointer-events: none;
}

.loading-content {
    text-align: center;
}

.loading-logo {
    margin-bottom: var(--space-lg);
    animation: pulse-glow 2s ease-in-out infinite;
}

.loading-logo-img {
    width: 160px;
    max-width: 80vw;
    height: auto;
    border-radius: 16px;
    filter: drop-shadow(0 0 25px rgba(183, 148, 246, 0.5));
    object-fit: contain;
}

.loading-bar {
    width: 200px;
    height: 4px;
    background: rgba(255, 255, 255, 0.15);
    border-radius: 4px;
    overflow: hidden;
    margin: 0 auto var(--space-md);
}

.loading-bar-fill {
    width: 0;
    height: 100%;
    background: var(--accent-gradient);
    border-radius: 4px;
    animation: loading-fill 1.5s ease-in-out forwards;
}

.loading-text {
    color: var(--text-secondary);
    font-size: 0.875rem;
    letter-spacing: 0.5px;
}

@keyframes loading-fill {
    0% { width: 0; }
    50% { width: 70%; }
    100% { width: 100%; }
}

@keyframes pulse-glow {
    0%, 100% { transform: scale(1); filter: drop-shadow(0 0 20px rgba(183, 148, 246, 0.4)); }
    50% { transform: scale(1.05); filter: drop-shadow(0 0 30px rgba(183, 148, 246, 0.7)); }
}

/* ── Particles Canvas ── */
#particles-canvas {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
}

/* ── Confetti Canvas ── */
#confetti-canvas {
    position: fixed;
    inset: 0;
    z-index: 9998;
    pointer-events: none;
}

/* ── App Container ── */
.app {
    position: relative;
    z-index: 1;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: opacity 0.5s ease;
}

.app.hidden {
    opacity: 0;
    pointer-events: none;
}

.app.visible {
    opacity: 1;
    pointer-events: auto;
}

/* ── Header ── */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(45, 27, 105, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--glass-border);
    padding: var(--space-md) var(--space-lg);
    transition: background var(--transition-speed) ease, box-shadow var(--transition-speed) ease;
}

body.light-theme .header {
    background: rgba(232, 224, 245, 0.85);
}

.header.scrolled {
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.2);
}

.header-content {
    max-width: 1100px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
}

.header-left {
    display: flex;
    align-items: center;
}

.logo-wrapper {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    cursor: default;
    transition: transform 0.3s ease;
}

.logo-wrapper:hover {
    transform: scale(1.02);
}

.header-logo-img {
    width: 44px;
    height: 44px;
    border-radius: 10px;
    object-fit: contain;
    filter: drop-shadow(0 0 12px var(--accent-glow));
    transition: filter 0.3s ease, transform 0.3s ease;
    flex-shrink: 0;
}

.logo-wrapper:hover .header-logo-img {
    filter: drop-shadow(0 0 20px rgba(183, 148, 246, 0.6));
}

.logo-text {
    display: flex;
    flex-direction: column;
}

.logo-title {
    font-size: 1.15rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    line-height: 1.2;
}

.logo-subtitle {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    font-weight: 400;
    letter-spacing: 0.02em;
}

.header-right {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

/* Theme Toggle */
.theme-toggle {
    position: relative;
    width: 44px;
    height: 44px;
    border: none;
    background: var(--surface);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    overflow: hidden;
}

.theme-toggle:hover {
    background: var(--surface-hover);
    transform: rotate(20deg);
}

.theme-icon {
    position: absolute;
    font-size: 1.2rem;
    transition: all 0.4s ease;
}

.theme-icon.moon {
    opacity: 1;
    transform: translateY(0) rotate(0);
}

.theme-icon.sun {
    opacity: 0;
    transform: translateY(20px) rotate(-90deg);
}

body.light-theme .theme-icon.moon {
    opacity: 0;
    transform: translateY(-20px) rotate(90deg);
}

body.light-theme .theme-icon.sun {
    opacity: 1;
    transform: translateY(0) rotate(0);
}

/* ── Main Content ── */
.main-content {
    flex: 1;
    max-width: 900px;
    width: 100%;
    margin: 0 auto;
    padding: var(--space-xl) var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

/* ── Tabs ── */
.tabs-container {
    display: flex;
    justify-content: center;
}

.tabs {
    display: flex;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: var(--border-radius);
    padding: 4px;
    gap: 4px;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.tab {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-lg);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-main);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: calc(var(--border-radius) - 4px);
    transition: all 0.3s ease;
    white-space: nowrap;
}

.tab:hover {
    color: var(--text-primary);
    background: var(--surface);
}

.tab.active {
    background: var(--accent-gradient);
    color: #fff;
    font-weight: 600;
    box-shadow: 0 4px 15px var(--accent-glow);
}

.tab-svg-icon {
    flex-shrink: 0;
    opacity: 0.85;
}

/* ── Panels ── */
.panel {
    display: none;
    animation: fadeSlideIn 0.4s ease forwards;
}

.panel.active {
    display: block;
}

@keyframes fadeSlideIn {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ── Glass Card ── */
.glass-card {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: var(--border-radius);
    padding: var(--space-xl);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    box-shadow: var(--glass-shadow);
    transition: all 0.3s ease;
}

.glass-card:hover {
    border-color: rgba(255, 255, 255, 0.18);
    box-shadow: 0 8px 40px rgba(0, 0, 0, 0.35);
}

body.light-theme .glass-card:hover {
    box-shadow: 0 8px 40px rgba(100, 60, 180, 0.15);
}

.card-title {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: var(--space-lg);
    letter-spacing: -0.01em;
}



/* ── Input Elements ── */
.input-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.input-label {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    letter-spacing: 0.03em;
    text-transform: uppercase;
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

.text-input {
    width: 100%;
    padding: 14px 16px;
    padding-right: 42px;
    background: var(--surface);
    border: 1.5px solid var(--glass-border);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 500;
    outline: none;
    transition: all 0.3s ease;
    letter-spacing: 0.05em;
}

.text-input::placeholder {
    color: var(--text-muted);
    font-weight: 400;
}

.text-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
    background: var(--surface-hover);
}

.text-input.error {
    border-color: var(--error-color);
    box-shadow: 0 0 0 3px rgba(255, 107, 107, 0.15);
}

.input-clear {
    position: absolute;
    right: 10px;
    width: 28px;
    height: 28px;
    border: none;
    background: var(--surface);
    color: var(--text-tertiary);
    border-radius: 50%;
    cursor: pointer;
    font-size: 0.85rem;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: all 0.2s ease;
}

.input-wrapper:hover .input-clear,
.text-input:focus ~ .input-clear {
    opacity: 1;
}

.input-clear:hover {
    background: var(--surface-active);
    color: var(--text-primary);
}

.select-input {
    width: 100%;
    padding: 14px 16px;
    background: var(--surface);
    border: 1.5px solid var(--glass-border);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-family: var(--font-main);
    font-size: 0.95rem;
    font-weight: 500;
    outline: none;
    cursor: pointer;
    transition: all 0.3s ease;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='rgba(255,255,255,0.5)' stroke-width='2.5'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 14px center;
    padding-right: 40px;
}

body.light-theme .select-input {
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='rgba(45,27,105,0.5)' stroke-width='2.5'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
}

.select-input option {
    background: #3D2E7C;
    color: #fff;
}

body.light-theme .select-input option {
    background: #fff;
    color: #2D1B69;
}

.select-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

/* ── Base Selectors ── */
.base-selectors {
    display: flex;
    align-items: flex-end;
    gap: var(--space-md);
    margin: var(--space-lg) 0;
}

.base-selectors .input-group {
    flex: 1;
}

.swap-btn {
    width: 44px;
    height: 44px;
    flex-shrink: 0;
    border: 1.5px solid var(--glass-border);
    background: var(--surface);
    color: var(--accent-primary);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    margin-bottom: 2px;
}

.swap-btn:hover {
    background: var(--accent-primary);
    color: #fff;
    border-color: var(--accent-primary);
    transform: rotate(180deg);
    box-shadow: 0 4px 15px var(--accent-glow);
}

/* ── Buttons ── */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 14px var(--space-xl);
    border: none;
    border-radius: var(--border-radius-sm);
    font-family: var(--font-main);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    letter-spacing: 0.01em;
    position: relative;
    overflow: hidden;
}

.btn::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(rgba(255,255,255,0.15), transparent);
    opacity: 0;
    transition: opacity 0.3s ease;
}

.btn:hover::after {
    opacity: 1;
}

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

.btn-primary {
    background: var(--accent-gradient);
    color: #fff;
    box-shadow: 0 4px 15px var(--accent-glow);
}

.btn-primary:hover {
    box-shadow: 0 6px 25px rgba(183, 148, 246, 0.45);
    transform: translateY(-1px);
}

.btn-primary:active {
    transform: translateY(0) scale(0.97);
}

.btn-secondary {
    background: var(--surface);
    color: var(--text-primary);
    border: 1.5px solid var(--glass-border);
}

.btn-secondary:hover {
    background: var(--surface-hover);
    border-color: var(--accent-primary);
}

.btn-ghost {
    background: transparent;
    color: var(--text-secondary);
    padding: var(--space-sm) var(--space-md);
    font-size: 0.85rem;
}

.btn-ghost:hover {
    color: var(--error-color);
    background: var(--error-bg);
}

.btn-convert {
    width: 100%;
    padding: 16px;
    font-size: 1.05rem;
}

.btn-icon {
    font-size: 1.1rem;
}

/* ── Calculator ── */
.operand-row {
    display: flex;
    align-items: flex-end;
    gap: var(--space-md);
    margin-bottom: var(--space-sm);
    animation: fadeSlideIn 0.3s ease forwards;
}

.operand-input-group {
    flex: 2;
}

.operand-base-group {
    flex: 1;
    min-width: 100px;
}

.operator-row {
    display: flex;
    justify-content: center;
    margin: var(--space-sm) 0;
}

.operator-select {
    padding: 8px 16px;
    background: var(--surface);
    border: 1.5px solid var(--glass-border);
    border-radius: 20px;
    color: var(--accent-primary);
    font-family: var(--font-main);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    outline: none;
    transition: all 0.3s ease;
    appearance: none;
    text-align: center;
    min-width: 140px;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='10' viewBox='0 0 24 24' fill='none' stroke='rgba(183,148,246,0.7)' stroke-width='2.5'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 30px;
}

.operator-select option {
    background: #3D2E7C;
    color: #fff;
}

body.light-theme .operator-select option {
    background: #fff;
    color: #2D1B69;
}

.operator-select:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.remove-operand-btn {
    width: 36px;
    height: 36px;
    flex-shrink: 0;
    border: none;
    background: var(--error-bg);
    color: var(--error-color);
    border-radius: 50%;
    cursor: pointer;
    font-size: 0.85rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    margin-bottom: 4px;
}

.remove-operand-btn:hover {
    background: var(--error-color);
    color: #fff;
    transform: scale(1.1);
}

.calc-actions {
    display: flex;
    gap: var(--space-md);
    margin-top: var(--space-lg);
}

.calc-actions .btn-secondary {
    flex: 0 0 auto;
}

.calc-actions .btn-primary {
    flex: 1;
}

/* ── Error Container ── */
.error-container {
    animation: shake 0.4s ease;
}

.error-card {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    background: var(--error-bg);
    border-color: rgba(255, 107, 107, 0.3);
}

.error-svg-icon {
    flex-shrink: 0;
    color: var(--error-color);
}

.error-message {
    color: var(--error-color);
    font-weight: 500;
    font-size: 0.95rem;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-8px); }
    40% { transform: translateX(8px); }
    60% { transform: translateX(-4px); }
    80% { transform: translateX(4px); }
}

/* ── Results Section ── */
.results-section {
    animation: fadeSlideIn 0.5s ease forwards;
}

.results-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
}

.result-item {
    background: var(--surface);
    border: 1px solid var(--glass-border);
    border-radius: var(--border-radius-sm);
    padding: var(--space-md);
    transition: all 0.3s ease;
    animation: resultPop 0.4s ease backwards;
}

.result-item:nth-child(1) { animation-delay: 0.05s; }
.result-item:nth-child(2) { animation-delay: 0.1s; }
.result-item:nth-child(3) { animation-delay: 0.15s; }
.result-item:nth-child(4) { animation-delay: 0.2s; }

@keyframes resultPop {
    from { opacity: 0; transform: scale(0.92) translateY(8px); }
    to { opacity: 1; transform: scale(1) translateY(0); }
}

.result-item:hover {
    background: var(--surface-hover);
    border-color: rgba(255, 255, 255, 0.2);
    transform: translateY(-2px);
}

.result-header {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
}

.result-badge {
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.result-badge.bin { background: rgba(255, 107, 157, 0.18); color: var(--bin-color); }
.result-badge.oct { background: rgba(255, 169, 77, 0.18); color: var(--oct-color); }
.result-badge.dec { background: rgba(105, 219, 124, 0.18); color: var(--dec-color); }
.result-badge.hex { background: rgba(116, 192, 252, 0.18); color: var(--hex-color); }

.result-label {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    font-weight: 400;
}

.result-value-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-sm);
}

.result-value {
    font-size: 1.25rem;
    font-weight: 600;
    word-break: break-all;
    line-height: 1.4;
}

.copy-btn {
    width: 32px;
    height: 32px;
    flex-shrink: 0;
    border: none;
    background: var(--surface);
    color: var(--text-tertiary);
    border-radius: var(--border-radius-xs);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.copy-btn:hover {
    background: var(--accent-primary);
    color: #fff;
    transform: scale(1.1);
}

.copy-btn.copied {
    background: var(--dec-color);
    color: #fff;
}

/* ── Steps Section ── */
.steps-section {
    animation: fadeSlideIn 0.5s ease forwards;
}

.steps-toggle {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0;
}

.steps-toggle .card-title {
    margin-bottom: 0;
}

.toggle-arrow {
    font-size: 0.9rem;
    color: var(--text-tertiary);
    transition: transform 0.3s ease;
}

.toggle-arrow.open {
    transform: rotate(180deg);
}

.steps-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease, padding 0.3s ease;
}

.steps-content.open {
    max-height: 2000px;
    padding-top: var(--space-lg);
}

.step-item {
    position: relative;
    padding: var(--space-md) var(--space-md) var(--space-md) var(--space-xl);
    margin-bottom: var(--space-sm);
    background: var(--surface);
    border-radius: var(--border-radius-xs);
    border-left: 3px solid var(--accent-primary);
    font-size: 0.9rem;
    line-height: 1.6;
    animation: fadeSlideIn 0.3s ease backwards;
}

.step-item:nth-child(odd) {
    border-left-color: var(--accent-secondary);
}

.step-number {
    position: absolute;
    left: 8px;
    top: 50%;
    transform: translateY(-50%);
    width: 22px;
    height: 22px;
    background: var(--accent-gradient);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.65rem;
    font-weight: 700;
    color: #fff;
}

.step-text {
    color: var(--text-secondary);
}

.step-text strong {
    color: var(--text-primary);
    font-weight: 600;
}

.step-text .highlight {
    color: var(--accent-primary);
    font-family: var(--font-mono);
    font-weight: 500;
}

/* ── History Section ── */
.history-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-md);
}

.history-header .card-title {
    margin-bottom: 0;
}

.history-list {
    max-height: 350px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
    scrollbar-width: thin;
    scrollbar-color: var(--surface-active) transparent;
}

.history-list::-webkit-scrollbar {
    width: 6px;
}

.history-list::-webkit-scrollbar-track {
    background: transparent;
}

.history-list::-webkit-scrollbar-thumb {
    background: var(--surface-active);
    border-radius: 3px;
}

.history-empty {
    text-align: center;
    padding: var(--space-xl) var(--space-md);
    color: var(--text-muted);
}

.empty-svg-icon {
    display: block;
    margin: 0 auto var(--space-sm);
    color: var(--text-muted);
}

.history-empty p {
    font-size: 0.9rem;
}

.history-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-md);
    background: var(--surface);
    border: 1px solid transparent;
    border-radius: var(--border-radius-xs);
    transition: all 0.2s ease;
    animation: fadeSlideIn 0.3s ease forwards;
    gap: var(--space-sm);
}

.history-item:hover {
    background: var(--surface-hover);
    border-color: var(--glass-border);
}

.history-item-content {
    display: flex;
    flex-direction: column;
    gap: 2px;
    flex: 1;
    min-width: 0;
}

.history-expression {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-primary);
    word-break: break-all;
}

.history-result {
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.history-time {
    font-size: 0.7rem;
    color: var(--text-muted);
    white-space: nowrap;
}

.history-delete {
    width: 28px;
    height: 28px;
    flex-shrink: 0;
    border: none;
    background: transparent;
    color: var(--text-muted);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    transition: all 0.2s ease;
}

.history-delete:hover {
    background: var(--error-bg);
    color: var(--error-color);
}

/* ── Shortcuts Section ── */
.shortcuts-card {
    padding: var(--space-lg);
}

.shortcuts-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: var(--space-md);
    color: var(--text-secondary);
}

.shortcuts-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-sm) var(--space-lg);
}

.shortcut-item {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.8rem;
    color: var(--text-tertiary);
}

kbd {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 3px 8px;
    background: var(--surface);
    border: 1px solid var(--glass-border);
    border-radius: 5px;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 500;
    color: var(--text-secondary);
    min-width: 28px;
    white-space: nowrap;
    box-shadow: 0 2px 0 rgba(0,0,0,0.15);
}

/* ── Footer ── */
.footer {
    border-top: 1px solid var(--glass-border);
    padding: var(--space-lg);
    margin-top: auto;
}

.footer-content {
    max-width: 1100px;
    margin: 0 auto;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-sm);
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.9rem;
}

.footer-logo-img {
    width: 26px;
    height: 26px;
    border-radius: 6px;
    object-fit: contain;
}

.footer-text {
    font-size: 0.8rem;
    color: var(--text-tertiary);
}

.heart {
    display: inline-block;
    animation: heartbeat 1.5s ease infinite;
}

@keyframes heartbeat {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.15); }
}

.footer-links {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.footer-link {
    color: var(--text-tertiary);
    text-decoration: none;
    font-size: 0.8rem;
    transition: color 0.2s ease;
}

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

.footer-separator {
    color: var(--text-muted);
    font-size: 0.7rem;
}

/* ── Toast Notification ── */
.toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-lg);
    background: rgba(45, 27, 105, 0.95);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: var(--border-radius-sm);
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.4);
    z-index: 10000;
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
    font-size: 0.9rem;
    font-weight: 500;
}

body.light-theme .toast {
    background: rgba(255, 255, 255, 0.95);
    color: var(--text-primary);
}

.toast.visible {
    transform: translateX(-50%) translateY(0);
}

.toast-svg-icon {
    flex-shrink: 0;
    color: var(--dec-color);
}

/* ── Utility Classes ── */
.hidden {
    display: none !important;
}

/* ── Responsive Design ── */

/* Tablet (768px - 1023px) */
@media (max-width: 1023px) {
    .main-content {
        padding: var(--space-lg) var(--space-md);
    }

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

    .header-logo-img {
        width: 38px;
        height: 38px;
    }

    .logo-title {
        font-size: 1.05rem;
    }
}

/* Mobile (< 768px) */
@media (max-width: 767px) {
    html {
        font-size: 15px;
    }

    .header {
        padding: var(--space-sm) var(--space-md);
    }

    .header-logo-img {
        width: 34px;
        height: 34px;
    }

    .logo-title {
        font-size: 0.95rem;
    }

    .logo-subtitle {
        font-size: 0.65rem;
    }

    .main-content {
        padding: var(--space-md) var(--space-sm);
        gap: var(--space-md);
    }

    .glass-card {
        padding: var(--space-lg) var(--space-md);
        border-radius: calc(var(--border-radius) - 2px);
    }

    .tab {
        padding: var(--space-sm) var(--space-md);
        font-size: 0.85rem;
    }

    .tab-icon {
        font-size: 1rem;
    }

    .base-selectors {
        flex-direction: column;
        gap: var(--space-sm);
    }

    .swap-btn {
        align-self: center;
        transform: rotate(90deg);
    }

    .swap-btn:hover {
        transform: rotate(270deg);
    }

    .results-grid {
        grid-template-columns: 1fr;
    }

    .result-value {
        font-size: 1.1rem;
    }

    .shortcuts-grid {
        grid-template-columns: 1fr 1fr;
        gap: var(--space-sm);
    }

    .shortcut-item {
        font-size: 0.7rem;
    }

    .calc-actions {
        flex-direction: column;
    }

    .operand-row {
        flex-wrap: wrap;
    }

    .operand-input-group {
        flex: 1 1 100%;
    }

    .operand-base-group {
        flex: 1;
    }

    .text-input {
        font-size: 1rem;
        padding: 12px 14px;
        padding-right: 38px;
    }

    .select-input {
        padding: 12px 14px;
        padding-right: 36px;
    }

    .btn-convert {
        padding: 14px;
    }

    .card-title {
        font-size: 1.05rem;
    }

    .footer-content {
        gap: var(--space-xs);
    }
}

/* Small Mobile (< 400px) */
@media (max-width: 399px) {
    html {
        font-size: 14px;
    }

    .logo-text {
        display: none;
    }

    .header-content {
        justify-content: center;
    }

    .header-right {
        position: absolute;
        right: var(--space-md);
    }

    .shortcuts-grid {
        grid-template-columns: 1fr;
    }

    .tabs {
        width: 100%;
    }

    .tab {
        flex: 1;
        justify-content: center;
    }
}

/* ── Animations for interactive elements ── */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ── Print Styles ── */
@media print {
    .header, .footer, .tabs-container, .history-section,
    .shortcuts-section, .theme-toggle, .copy-btn,
    .btn-convert, .btn-secondary, #particles-canvas, #confetti-canvas,
    .loading-screen {
        display: none !important;
    }

    body {
        background: #fff;
        color: #000;
    }

    .glass-card {
        background: #f5f5f5;
        border: 1px solid #ddd;
        box-shadow: none;
        backdrop-filter: none;
    }
}