/* css/style.css */
:root {
    --bg-dark: #0b0f1a;
    --surface-light: rgba(255, 255, 255, 0.05);
    --border-color: rgba(255, 255, 255, 0.12);
    --accent-cyan: #00f2ff;
    --accent-purple: #7000ff;
    --accent-pink: #ff007b;
    --accent-glow: rgba(0, 242, 255, 0.3);
    --text-main: #ffffff;
    --text-muted: #94a3b8;
    --radius-md: 14px;
}

*, *::before, *::after {
    box-sizing: border-box;
}

body {
    font-family: 'Inter', sans-serif;
    background: radial-gradient(circle at top right, #1a0b2e, #0b0f1a 65%);
    color: var(--text-main);
    min-height: 100vh;
    margin: 0;
    padding: 0;
}

/* common container */
.app-container {
    padding: 2rem 1.5rem 3rem;
    max-width: 1200px;
    margin: 0 auto;
}

/* header & title */
.app-header {
    text-align: center;
    margin-bottom: 2rem;
    position: relative;
    padding-top: 10px;
}

.app-title {
    font-size: 2.4rem;
    font-weight: 900;
    background: linear-gradient(90deg, var(--accent-cyan), #a855f7, var(--accent-pink));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin: 0 0 0.6rem 0;
    letter-spacing: -0.5px;
}

.app-subtitle {
    color: var(--text-muted);
    max-width: 720px;
    margin: 0 auto;
    line-height: 1.55;
    font-size: 1rem;
}

/* Back Button */
.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    position: absolute;
    left: 0;
    top: 5px;
    color: var(--text-muted);
    text-decoration: none;
    font-weight: 600;
    padding: 8px 16px;
    border-radius: 10px;
    background: var(--surface-light);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
    backdrop-filter: blur(8px);
}

.back-btn:hover {
    color: var(--text-main);
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-cyan);
    box-shadow: 0 0 15px var(--accent-glow);
    transform: translateX(-3px);
}

.back-btn svg {
    width: 20px;
    height: 20px;
    fill: currentColor;
}

/* Common form elements */
.form-group {
    margin-bottom: 1.25rem;
}

.form-label {
    display: block;
    margin-bottom: 0.45rem;
    color: var(--text-muted);
    font-size: 0.88rem;
    font-weight: 600;
}

.form-control {
    width: 100%;
    background: rgba(8, 12, 22, 0.65);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.7rem 0.85rem;
    color: var(--text-main);
    outline: none;
    font-family: inherit;
    font-size: 0.95rem;
}

.form-control:focus {
    border-color: var(--accent-cyan);
    box-shadow: 0 0 10px rgba(0, 242, 255, 0.2);
}

input[type="range"] {
    accent-color: var(--accent-cyan);
    cursor: pointer;
}

/* Button style */
.primary-btn {
    background: linear-gradient(135deg, var(--accent-cyan), #00a2ff);
    color: #050811;
    border: none;
    padding: 0.9rem 1.8rem;
    border-radius: 10px;
    font-weight: 800;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    text-transform: uppercase;
    display: inline-block;
    text-align: center;
    letter-spacing: 0.4px;
}

.primary-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px var(--accent-glow);
}

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

@media (max-width: 820px) {
    .back-btn {
        position: static;
        margin-bottom: 1rem;
    }
    .app-title {
        font-size: 1.85rem;
    }
}