:root {
    --bg-gradient: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    --card-bg: rgba(255, 255, 255, 0.05);
    --card-border: rgba(255, 255, 255, 0.1);
    --card-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-color: #38bdf8;
    --accent-hover: #0ea5e9;
    --danger-color: #ef4444;
    --input-bg: rgba(0, 0, 0, 0.2);
    --input-border: rgba(255, 255, 255, 0.08);
    --radius-lg: 24px;
    --radius-md: 16px;
    --radius-sm: 8px;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font-family);
    background: var(--bg-gradient);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow-x: hidden;
}

.app-container {
    width: 100%;
    max-width: 480px;
    min-height: 100vh;
    padding: 24px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

/* Header */
header {
    margin-bottom: 24px;
    text-align: center;
    animation: fadeInDown 0.8s ease-out;
}

.logo-container {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
}

.logo-icon {
    width: 42px;
    height: 42px;
    background: linear-gradient(135deg, var(--accent-color), #2563eb);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px rgba(56, 189, 248, 0.3);
}

h1 {
    font-size: 20px;
    font-weight: 700;
    letter-spacing: -0.5px;
    background: linear-gradient(to right, #fff, #94a3b8);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    font-size: 13px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Main Card */
.converter-card {
    background: var(--card-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--card-shadow);
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
    animation: fadeInUp 0.8s ease-out 0.2s backwards;
}

/* Select */
.controls-row {
    position: relative;
    z-index: 10;
}

.select-wrapper {
    position: relative;
    width: 100%;
}

select {
    width: 100%;
    appearance: none;
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    font-family: inherit;
    font-size: 16px;
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    outline: none;
}

select:focus,
select:hover {
    border-color: var(--accent-color);
    background: rgba(255, 255, 255, 0.08);
}

/* Fix for dropdown options visibility */
select option {
    background-color: #1e293b;
    /* Dark slate background */
    color: #f8fafc;
    /* Light text */
}

.select-arrow {
    position: absolute;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    pointer-events: none;
    color: var(--text-secondary);
}

/* Toggle */
.toggle-container {
    display: flex;
    background: var(--input-bg);
    padding: 4px;
    border-radius: var(--radius-md);
    border: 1px solid var(--input-border);
}

.toggle-btn {
    flex: 1;
    background: transparent;
    border: none;
    padding: 10px;
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 14px;
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition);
}

.toggle-btn.active {
    background: var(--accent-color);
    color: white;
    box-shadow: 0 2px 8px rgba(56, 189, 248, 0.4);
}

/* Caesar Controls */
.caesar-controls {
    display: flex;
    flex-direction: column;
    gap: 8px;
    padding: 12px;
    background: rgba(56, 189, 248, 0.1);
    border-radius: var(--radius-md);
    border: 1px solid rgba(56, 189, 248, 0.2);
    transition: var(--transition);
}

.caesar-controls.hidden {
    display: none;
}

.caesar-controls label {
    font-size: 13px;
    color: var(--accent-color);
    font-weight: 600;
    display: flex;
    justify-content: space-between;
}

input[type=range] {
    width: 100%;
    accent-color: var(--accent-color);
    cursor: pointer;
}

/* Input/Output */
.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
    flex: 1;
}

.label-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

label {
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

textarea {
    width: 100%;
    height: 120px;
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: var(--radius-md);
    padding: 16px;
    font-family: 'JetBrains Mono', 'Roboto Mono', monospace;
    font-size: 15px;
    color: var(--text-primary);
    resize: none;
    transition: var(--transition);
    outline: none;
    line-height: 1.5;
}

textarea:focus {
    border-color: var(--accent-color);
    background: rgba(0, 0, 0, 0.4);
}

textarea[readonly] {
    background: rgba(0, 0, 0, 0.1);
    cursor: default;
    color: var(--accent-color);
}

/* Buttons */
.action-buttons {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 12px;
}

.primary-btn,
.secondary-btn,
.icon-btn {
    border: none;
    border-radius: var(--radius-md);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-family: inherit;
}

.primary-btn {
    background: linear-gradient(135deg, var(--accent-color), #2563eb);
    color: white;
    padding: 14px;
    font-size: 16px;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.primary-btn:active {
    transform: scale(0.98);
}

.secondary-btn {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-secondary);
    border: 1px solid var(--input-border);
}

.secondary-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: white;
}

.icon-btn {
    background: transparent;
    color: var(--text-secondary);
    padding: 4px;
    border-radius: 6px;
}

.icon-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--accent-color);
    transform: translateY(-2px);
}

/* Footer */
footer {
    text-align: center;
    margin-top: 24px;
    color: var(--text-secondary);
    font-size: 12px;
    opacity: 0.6;
}

/* Animations */
@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Mobile Optimizations */
@media (max-width: 480px) {
    .app-container {
        padding: 16px;
    }

    .converter-card {
        padding: 20px;
        gap: 16px;
    }

    textarea {
        height: 100px;
    }
}

/* Tabs */
.tab-nav {
    display: flex;
    background: var(--input-bg);
    padding: 4px;
    border-radius: var(--radius-md);
    margin-bottom: 20px;
    border: 1px solid var(--input-border);
}

.tab-btn {
    flex: 1;
    background: transparent;
    border: none;
    padding: 12px;
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 14px;
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.tab-btn.active {
    background: rgba(255, 255, 255, 0.1);
    color: white;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease-out;
}

.tab-content.active {
    display: flex;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(5px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Base Converter Specifics */
.base-select-group {
    display: flex;
    align-items: flex-end;
    gap: 12px;
    width: 100%;
}

.exchange-icon {
    padding-bottom: 12px;
    /* Align with inputs */
}

/* Mobile tweak for base group */
@media (max-width: 480px) {
    .base-select-group {
        flex-direction: column;
        align-items: stretch;
    }

    .exchange-icon {
        align-self: center;
        padding-bottom: 0;
        transform: rotate(90deg);
    }
}