:root {
    --bg-color: #f0f0f0;
    --text-color: #333;
    --board-bg: #fff;
    --board-border: #000;
    --button-bg: #007bff;
    --button-text: #fff;
    --button-hover: #0056b3;
}

[data-theme='dark'] {
    --bg-color: #121212;
    --text-color: #e0e0e0;
    --board-bg: #1e1e1e;
    --board-border: #333;
    --button-bg: #3700b3;
    --button-text: #fff;
    --button-hover: #1f0064;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 40px 0;
    min-height: 100vh;
    box-sizing: border-box;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

#username-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

#username-box {
    background-color: var(--board-bg);
    padding: 30px;
    border-radius: 10px;
    text-align: center;
    border: 2px solid var(--board-border);
}

#username-input {
    padding: 10px;
    font-size: 1.1rem;
    width: 80%;
    margin: 20px 0;
    border-radius: 5px;
    border: 1px solid var(--board-border);
    background-color: var(--bg-color);
    color: var(--text-color);
}

#save-username-btn {
    padding: 10px 30px;
    font-size: 1.1rem;
    cursor: pointer;
    background-color: var(--button-bg);
    color: var(--button-text);
    border: none;
    border-radius: 5px;
    transition: background-color 0.2s;
}

#save-username-btn:hover {
    background-color: var(--button-hover);
}

#game-wrapper {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: flex-start;
    gap: 30px;
    max-width: 900px;
}

#game-container {
    text-align: center;
    padding: 20px;
    background: transparent;
}

#side-panel {
    display: flex;
    flex-direction: column;
    gap: 20px;
    width: 250px;
}

#leaderboard-container {
    background-color: var(--board-bg);
    padding: 20px;
    border-radius: 10px;
    border: 2px solid var(--board-border);
    text-align: center;
}

#leaderboard-list {
    list-style: none;
    padding: 0;
    margin-top: 15px;
    text-align: left;
}

#leaderboard-list li {
    padding: 8px 0;
    border-bottom: 1px solid #eee;
    display: flex;
    justify-content: space-between;
}

#leaderboard-list li:last-child {
    border-bottom: none;
}

#controls-panel {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    background-color: var(--board-bg);
    padding: 20px;
    border-radius: 10px;
    border: 2px solid var(--board-border);
}

.control-row {
    display: flex;
    gap: 10px;
}

.control-btn {
    width: 60px;
    height: 60px;
    font-size: 1.2rem;
    font-weight: bold;
    cursor: pointer;
    border: none;
    border-radius: 50%;
    background-color: var(--button-bg);
    color: var(--button-text);
    display: flex;
    justify-content: center;
    align-items: center;
    user-select: none;
    touch-action: manipulation;
    transition: background-color 0.1s, transform 0.1s;
}

.control-btn:active {
    background-color: var(--button-hover);
    transform: scale(0.95);
}

#btn-up, #btn-space {
    width: 120px;
    border-radius: 10px;
}

#tetris-board {
    border: 4px solid var(--board-border);
    background-color: var(--board-bg);
    box-shadow: 0 0 20px rgba(0,0,0,0.1);
}

#info {
    margin-top: 20px;
}

#start-button, #pause-button, #theme-toggle {
    padding: 12px 24px;
    font-size: 16px;
    cursor: pointer;
    border: none;
    border-radius: 4px;
    background-color: var(--button-bg);
    color: var(--button-text);
    transition: background-color 0.2s;
    margin: 5px;
}

#start-button:hover, #pause-button:hover, #theme-toggle:hover {
    background-color: var(--button-hover);
}

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