:root {
    /* Default (Gaming) Theme */
    --bg-color: #1a1a1a;
    --app-bg: rgba(255, 255, 255, 0.05);
    --app-border: 1px solid rgba(255, 255, 255, 0.1);
    --app-shadow: 0 0 40px rgba(0, 255, 255, 0.2), 0 0 80px rgba(255, 0, 255, 0.2);
    --text-color: #e0e0e0;
    --header-shadow: 0 0 10px rgba(0, 255, 255, 0.7), 0 0 20px rgba(255, 0, 255, 0.7);
    --label-color: #00ffff;
    --input-bg: rgba(0, 0, 0, 0.5);
    --input-border: 1px solid #00ffff;
    --input-focus-shadow: 0 0 15px rgba(0, 255, 255, 0.5);
    --button-gradient: linear-gradient(45deg, #00ffff, #ff00ff);
    --button-hover-shadow: 0 0 20px rgba(0, 255, 255, 0.7), 0 0 30px rgba(255, 0, 255, 0.7);
    --result-border: 1px solid rgba(255, 255, 255, 0.1);
    --result-row-bg: rgba(0, 0, 0, 0.3);
    --total-shadow: 0 0 10px #ff00ff;
}

body[data-theme="dark"] {
    --bg-color: #121212;
    --app-bg: #1e1e1e;
    --app-border: 1px solid #333;
    --app-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --text-color: #f0f0f0;
    --header-shadow: 0 0 8px rgba(76, 175, 80, 0.7);
    --label-color: #4CAF50;
    --input-bg: #2c2c2c;
    --input-border: 1px solid #4CAF50;
    --input-focus-shadow: 0 0 10px rgba(76, 175, 80, 0.5);
    --button-gradient: linear-gradient(45deg, #4CAF50, #81C784);
    --button-hover-shadow: 0 0 15px rgba(76, 175, 80, 0.7);
    --result-border: 1px solid #333;
    --result-row-bg: #2c2c2c;
    --total-shadow: 0 0 8px #4CAF50;
}

body[data-theme="white"] {
    --bg-color: #f4f4f9;
    --app-bg: #ffffff;
    --app-border: 1px solid #ddd;
    --app-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.17);
    --text-color: #333333;
    --header-shadow: none;
    --label-color: #007bff;
    --input-bg: #ffffff;
    --input-border: 1px solid #ced4da;
    --input-focus-shadow: 0 0 5px rgba(0, 123, 255, 0.5);
    --button-gradient: linear-gradient(45deg, #007bff, #0056b3);
    --button-hover-shadow: 0 5px 15px rgba(0, 123, 255, 0.4);
    --result-border: 1px solid #eee;
    --result-row-bg: #f8f9fa;
    --total-shadow: none;
}

body {
    font-family: 'Noto Sans KR', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s, color 0.3s;
}

.theme-switcher {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

#theme-toggle-btn {
    background: var(--app-bg);
    border: 1px solid var(--label-color);
    color: var(--text-color);
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    width: 50px;
    height: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all 0.3s ease;
}

#theme-toggle-btn:hover {
    box-shadow: var(--button-hover-shadow);
}

#app {
    background: var(--app-bg);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    border: var(--app-border);
    padding: 2.5rem;
    width: 100%;
    max-width: 700px;
    box-shadow: var(--app-shadow);
    transition: background-color 0.3s;
}

h1, h2 {
    font-family: 'Orbitron', sans-serif;
    text-align: center;
    text-shadow: var(--header-shadow);
}

.form-group {
    margin-bottom: 2rem;
}

label {
    display: block;
    margin-bottom: 0.75rem;
    font-weight: bold;
    text-transform: uppercase;
    font-size: 0.9rem;
    color: var(--label-color);
}

input,
select {
    width: 100%;
    padding: 1rem;
    background: var(--input-bg);
    border: var(--input-border);
    border-radius: 10px;
    color: var(--text-color);
    box-sizing: border-box;
    transition: all 0.3s ease;
}

input:focus,
select:focus {
    outline: none;
    box-shadow: var(--input-focus-shadow);
}

button {
    width: 100%;
    padding: 1.25rem;
    background: var(--button-gradient);
    color: white;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 2px;
    transition: all 0.3s ease;
}

button:hover {
    box-shadow: var(--button-hover-shadow);
    transform: translateY(-3px);
}

.result {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: var(--result-border);
}

.result-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0 10px;
    margin-top: 2rem;
}

.result-table th,
.result-table td {
    padding: 1rem;
    border: none;
    text-align: left;
}

.result-table tr {
    background: var(--result-row-bg);
    border-radius: 8px;
}

.result-table th {
    color: var(--label-color);
    text-transform: uppercase;
    font-size: 0.9rem;
    border-bottom: 2px solid var(--label-color);
}

.total {
    margin-top: 2rem;
    text-align: right;
    font-size: 1.5rem;
    font-weight: bold;
    font-family: 'Orbitron', sans-serif;
    text-shadow: var(--total-shadow);
}

/* Floating Back Button Styles */
#floating-back-btn-container {
    position: fixed;
    bottom: 30px;
    right: 30px;
    z-index: 2000;
}

.floating-btn {
    background: var(--app-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--label-color);
    color: var(--text-color);
    padding: 0.75rem 1.5rem;
    border-radius: 50px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 10px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    width: auto; /* Override default button width */
}

.floating-btn:hover {
    transform: translateY(-5px) scale(1.05);
    box-shadow: var(--button-hover-shadow);
    background: var(--button-gradient);
    color: white;
}

.floating-btn .icon {
    font-size: 1.2rem;
}

.floating-btn .text {
    font-weight: bold;
    font-size: 1rem;
    letter-spacing: 1px;
}