:root {
    --bg-color: #121418;
    --card-bg: rgba(255, 255, 255, 0.05);
    --card-border: rgba(255, 255, 255, 0.1);
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
    --accent-color: #00f2ff;
    /* Cyan Neon */
    --accent-glow: rgba(0, 242, 255, 0.2);
    --input-bg: rgba(0, 0, 0, 0.3);
    --font-heading: 'Inter', sans-serif;
    --font-mono: 'Roboto Mono', monospace;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-heading);
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    /* No scrolling */
}

.app-container {
    width: 100%;
    max-width: 480px;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 24px;
    position: relative;
}

header {
    text-align: center;
    margin-bottom: 10px;
}

header h1 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 8px;
    background: linear-gradient(90deg, #fff, #a0a0a0);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

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

.card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 16px;
    padding: 20px;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
}

.input-group label {
    display: block;
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.input-wrapper {
    display: flex;
    align-items: center;
    background: var(--input-bg);
    border-radius: 12px;
    padding: 4px 16px;
    border: 1px solid transparent;
    transition: all 0.3s ease;
}

.input-wrapper:focus-within {
    border-color: var(--accent-color);
    box-shadow: 0 0 15px var(--accent-glow);
}

input[type="number"] {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 1.8rem;
    padding: 12px 0;
    outline: none;
    width: 100%;
    -moz-appearance: textfield;
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

.unit {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-weight: 600;
    margin-left: 10px;
}

/* Toggle Switch */
.toggle-container {
    display: flex;
    position: relative;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    padding: 4px;
    margin-left: 10px;
}

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

.toggle-container label {
    z-index: 1;
    padding: 8px 12px;
    cursor: pointer;
    font-size: 0.9rem;
    color: var(--text-secondary);
    transition: color 0.3s;
    margin-bottom: 0;
}

.toggle-container input[type="radio"]:checked+label {
    color: var(--bg-color);
    font-weight: 700;
}

.slider {
    position: absolute;
    top: 4px;
    bottom: 4px;
    left: 4px;
    width: calc(50% - 4px);
    background: var(--accent-color);
    border-radius: 6px;
    transition: transform 0.3s ease;
}

#unit-l:checked~.slider {
    transform: translateX(100%);
}

/* Navigation Button */
.nav-btn {
    align-self: flex-end;
    /* Places it at the top right of the flex column */
    margin-bottom: -10px;
    /* Slight pull to keep it tight with header */
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    text-decoration: none;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.75rem;
    border: 1px solid var(--card-border);
    transition: all 0.3s ease;
    z-index: 10;
}

.nav-btn:hover {
    background: var(--accent-color);
    color: #000;
    box-shadow: 0 0 15px var(--accent-glow);
}

/* Output Section */
.output-group {
    background: rgba(0, 0, 0, 0.5);
    /* Darker for contrast */
    text-align: center;
    border: 1px solid var(--accent-color);
    box-shadow: 0 0 20px var(--accent-glow);
    position: relative;
    /* Context for Reset Btn */
    padding-bottom: 40px;
    /* Space for reset button */
}

.output-label {
    text-transform: uppercase;
    font-size: 0.8rem;
    letter-spacing: 2px;
    color: var(--accent-color);
    margin-bottom: 10px;
}

.result-display {
    font-family: var(--font-mono);
    font-size: 3rem;
    color: #fff;
    font-weight: 700;
    display: flex;
    justify-content: center;
    align-items: baseline;
    gap: 10px;
}

.result-unit {
    font-size: 1.5rem;
    color: var(--text-secondary);
}

/* Reset Button */
#reset-btn {
    position: absolute;
    bottom: 10px;
    right: 50%;
    transform: translateX(50%);
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    opacity: 0.6;
    transition: opacity 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 5px;
}

#reset-btn:hover {
    opacity: 1;
    color: var(--accent-color);
}

footer {
    text-align: center;
    margin-top: auto;
}

footer p {
    font-size: 0.75rem;
    color: #666;
    max-width: 90%;
    margin: 0 auto;
}