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

:root {
    --bg: #1a1a2e;
    --header-bg: #16213e;
    --card-bg: #d5e4de;
    --card-hover: #c2d8d0;
    --x-color: #e94560;
    --o-color: #4a90d9;
    --border-color: #0f3460;
    --text-light: #eaeaea;
    --accent: #e94560;
}

body {
    font-family: "Poppins", sans-serif;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    background: var(--bg);
    color: var(--text-light);
}

/* Header */
header {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 0.3rem;
    padding: 1rem;
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: 2px;
    color: var(--text-light);
}

header .score {
    font-size: 0.95rem;
    color: #aaa;
}

header .turn {
    font-size: 1rem;
    font-weight: 600;
}

/* Game grid */
.game-container {
    width: min(80vh, 80vw);
    aspect-ratio: 1;
    display: grid;
    gap: 10px;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    padding: 10px;
    background: var(--border-color);
    border-radius: 16px;
}

.square {
    background: var(--card-bg);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(2rem, 8vw, 4rem);
    font-weight: 700;
    cursor: pointer;
    transition: background 0.15s;
}

.square:hover {
    background: var(--card-hover);
}

.square[data-mark="X"] {
    color: var(--x-color);
    cursor: default;
}

.square[data-mark="X"]:hover {
    background: var(--card-bg);
}

.square[data-mark="O"] {
    color: var(--o-color);
    cursor: default;
}

.square[data-mark="O"]:hover {
    background: var(--card-bg);
}

/* Footer */
.game-end {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.game-end .message {
    font-size: 1.1rem;
    font-weight: 600;
    min-height: 1.5rem;
}

#restart {
    padding: 0.5rem 1.5rem;
    font-family: "Poppins", sans-serif;
    font-size: 0.95rem;
    font-weight: 600;
    background: var(--accent);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: opacity 0.2s;
}

#restart:hover {
    opacity: 0.85;
}

/* Dialog */
dialog {
    border: none;
    border-radius: 16px;
    padding: 2rem;
    width: 90%;
    max-width: 360px;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.4);
    margin: auto;
    background: var(--header-bg);
    color: var(--text-light);
}

dialog::backdrop {
    background: rgba(0, 0, 0, 0.6);
}

.player-dialog h2 {
    margin-bottom: 1.2rem;
    font-size: 1.2rem;
    text-align: center;
}

.player-dialog label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 0.3rem;
    color: #aaa;
}

.player-dialog input {
    width: 100%;
    padding: 0.5rem 0.75rem;
    font-family: "Poppins", sans-serif;
    font-size: 1rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background: var(--bg);
    color: var(--text-light);
    margin-bottom: 1.2rem;
}

.mark-select {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.mark-select p {
    font-size: 0.9rem;
    color: #aaa;
}

.mark-select button {
    width: 100%;
    padding: 0.6rem;
    font-family: "Poppins", sans-serif;
    font-size: 1.1rem;
    font-weight: 700;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: opacity 0.2s;
}

#player-marker-x {
    background: var(--x-color);
    color: white;
}

#player-marker-o {
    background: var(--o-color);
    color: white;
}

.mark-select button:hover {
    opacity: 0.85;
}