@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@400;700;900&family=Poppins:wght@600;700&display=swap');

:root {
    --noise-url: url("data:image/svg+xml,%3Csvg viewBox='0 0 400 400' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
}

[data-theme='dark'] {
    --bg-color: #1a1a1d;
    --surface-color: #2c2c34;
    --primary-color: #4a90e2;
    --primary-glow: rgba(74, 144, 226, 0.4);
    --accent-color: #50e3c2;
    --accent-glow: rgba(80, 227, 194, 0.4);
    --text-color: #f2f2f7;
    --text-muted-color: #a9a9b3;
    --button-text-color: #1a1a1d;
    --app-shadow: 0px 8px 24px rgba(0, 0, 0, 0.4);
}

[data-theme='light'] {
    --bg-color: #f0f2f5;
    --surface-color: #ffffff;
    --primary-color: #3b82f6;
    --primary-glow: rgba(59, 130, 246, 0.3);
    --accent-color: #10b981;
    --accent-glow: rgba(16, 185, 129, 0.3);
    --text-color: #1f2937;
    --text-muted-color: #6b7280;
    --button-text-color: #ffffff;
    --app-shadow: 0px 8px 24px rgba(60, 60, 80, 0.12);
}

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

body::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background-image: var(--noise-url);
    opacity: 0.05;
    pointer-events: none;
    z-index: -1;
}

#app {
    width: 90%;
    max-width: 500px;
    text-align: center;
    background: var(--surface-color);
    padding: 2rem 2.5rem 3rem;
    border-radius: 24px;
    border: 1px solid rgba(128, 128, 128, 0.1);
    box-shadow: var(--app-shadow);
    transition: background-color 0.3s, transform 0.3s ease, box-shadow 0.3s ease;
    position: relative;
}

#theme-switcher {
    position: absolute;
    top: 20px;
    right: 20px;
}

#theme-toggle-btn {
    cursor: pointer;
    color: var(--text-muted-color);
    transition: color 0.2s;
}

#theme-toggle-btn:hover {
    color: var(--primary-color);
}

h1 {
    font-weight: 700;
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

#level-selection p {
    color: var(--text-muted-color);
    font-size: 1.1rem;
    margin-bottom: 1.5rem;
}

.radio-group {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 2rem;
}

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

.radio-group label {
    padding: 0.6rem 1.2rem;
    border: 2px solid var(--primary-color);
    border-radius: 50px;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    font-weight: 600;
    color: var(--primary-color);
}

.radio-group input[type="radio"]:checked + label {
    background-color: var(--primary-color);
    color: var(--button-text-color);
    box-shadow: 0 0 15px var(--primary-glow);
}

#word-container {
    margin-top: 1rem;
    padding: 3rem 1rem 1rem;
    background: rgba(0,0,0,0.05);
    border-radius: 16px;
    min-height: 280px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    position: relative;
}

#word-counter {
    position: absolute;
    top: 1rem;
    left: 0;
    right: 0;
    text-align: center;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-muted-color);
}

#kanji {
    font-family: 'Noto Sans JP', sans-serif;
    font-weight: 400;
    font-size: 6rem;
    line-height: 1.2;
    color: var(--text-color);
    width: 100%;
    word-break: keep-all;
    text-align: center;
    margin: 0;
}

#hiragana {
    font-family: 'Noto Sans JP', sans-serif;
    font-size: 1.75rem;
    color: var(--text-muted-color);
    font-weight: 400;
    margin-top: 0.75rem;
    line-height: 1.5;
}

#meaning {
    font-family: 'Noto Sans JP', sans-serif;
    font-size: 1.75rem;
    color: var(--text-muted-color);
    font-weight: 400;
    margin-top: 0.03rem;
    line-height: 1;
}

#controls {
    margin-top: 2rem;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1rem;
}

button {
    padding: 1rem 1.8rem;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 700;
    font-family: 'Poppins', sans-serif;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    color: var(--button-text-color);
    position: relative;
}

#start-btn, #show-hiragana-btn, #show-meaning-btn, #copy-btn {
    background-color: var(--primary-color);
}

#next-word-btn {
    background-color: var(--accent-color);
}

button:hover {
    transform: translateY(-3px) scale(1.05);
}

#start-btn:hover, #show-hiragana-btn:hover, #show-meaning-btn:hover, #copy-btn:hover {
    box-shadow: 0 5px 20px var(--primary-glow);
}

#next-word-btn:hover {
    box-shadow: 0 5px 20px var(--accent-glow);
}

.hidden {
    display: none !important;
}

#word-list {
    width: 100%;
    box-sizing: border-box;
    height: 150px;
    margin-top: 1.5rem;
    padding: 1rem;
    border-radius: 8px;
    border: 1px solid var(--primary-color);
    background: var(--bg-color);
    color: var(--text-color);
    font-size: 1rem;
}

/* 반응형 디자인 */
@media (max-width: 480px) {
    #app { padding: 1.5rem 1rem 2rem; }
    h1 { font-size: 2rem; }
    #kanji { font-size: 4.5rem; }
    #hiragana, #meaning { font-size: 1.4rem; }
    button { padding: 0.8rem 1.2rem; }
    .radio-group label { padding: 0.5rem 1rem; }
}