:root {
    --bg-color: #0f172a;
    --text-color: #f8fafc;
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --danger-color: #ef4444;
    --danger-hover: #dc2828;
    --success-color: #10b981;
    --accent-color: #f59e0b;
    --card-bg: #1e293b;
}

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

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden; /* Prevent scrolling during gameplay */
}

#game-container {
    width: 100%;
    max-width: 800px;
    height: 100vh;
    max-height: 600px;
    position: relative;
    background-color: var(--bg-color);
    box-shadow: 0 0 50px rgba(0,0,0,0.5);
    border-radius: 12px;
    overflow: hidden;
}

/* Screens */
.screen {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 2rem;
    background: radial-gradient(circle at center, #1e293b 0%, #0f172a 100%);
}

.screen.active {
    display: flex;
}

h1 {
    font-size: 5rem;
    font-weight: 800;
    margin-bottom: 2.5rem;
    color: var(--accent-color);
    text-shadow: 0 4px 20px rgba(245, 158, 11, 0.4);
    letter-spacing: 2px;
}

h2 {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
    text-shadow: 0 2px 10px rgba(59, 130, 246, 0.3);
}

/* Buttons */
.menu-buttons {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.btn {
    padding: 1.2rem 2.5rem;
    font-size: 1.5rem;
    font-weight: 600;
    font-family: inherit;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.2s ease;
    background-color: var(--primary-color);
    color: white;
    width: 250px;
    margin: 0.6rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.3);
}

.btn:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.4);
}

.btn:active {
    transform: translateY(1px);
}

.difficulty-btn[data-diff="easy"] { background-color: var(--success-color); }
.difficulty-btn[data-diff="medium"] { background-color: var(--accent-color); }
.difficulty-btn[data-diff="hard"] { background-color: var(--danger-color); }

.difficulty-btn[data-diff="easy"]:hover { background-color: #059669; }
.difficulty-btn[data-diff="medium"]:hover { background-color: #d97706; }
.difficulty-btn[data-diff="hard"]:hover { background-color: var(--danger-hover); }

.shop-btn {
    background-color: #8b5cf6;
    margin-top: 1rem;
}
.shop-btn:hover { background-color: #7c3aed; }

/* HUD */
#hud {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 10;
    background: linear-gradient(to bottom, rgba(15,23,42,0.9) 0%, transparent 100%);
    pointer-events: none;
}

.hud-item {
    font-size: 1.2rem;
    font-weight: 600;
    text-shadow: 0 2px 4px rgba(0,0,0,0.8);
}

.timer-warning {
    color: var(--danger-color);
    font-size: 1.5rem;
    font-weight: 800;
}

#hud-weapon {
    color: var(--accent-color);
    animation: pulse 1s infinite alternate;
}

@keyframes pulse {
    0% { transform: scale(1); opacity: 0.8; }
    100% { transform: scale(1.1); opacity: 1; text-shadow: 0 0 10px var(--accent-color); }
}

@keyframes pop {
    0% { transform: scale(1); }
    50% { transform: scale(1.6); color: var(--accent-color); }
    100% { transform: scale(1); }
}

.pop-anim {
    display: inline-block;
    animation: pop 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

/* Canvas */
#game-canvas {
    width: 100%;
    height: 100%;
    display: block;
    background-color: #1e293b;
}

/* Shop */
#shop-screen {
    justify-content: flex-start;
    overflow-y: auto;
}

.stats {
    font-size: 2rem;
    margin-bottom: 2.5rem;
    color: var(--accent-color);
    font-weight: bold;
}

.shop-items {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    width: 100%;
    max-width: 900px;
    margin-bottom: 2rem;
}

.shop-category h3 {
    margin-bottom: 1.2rem;
    font-size: 1.8rem;
    border-bottom: 3px solid var(--primary-color);
    padding-bottom: 0.5rem;
}

.shop-item {
    display: block;
    width: 100%;
    padding: 1.2rem;
    margin-bottom: 0.8rem;
    background-color: var(--card-bg);
    color: var(--text-color);
    border: 2px solid var(--primary-color);
    border-radius: 8px;
    cursor: pointer;
    font-family: inherit;
    font-weight: 600;
    font-size: 1.3rem;
    transition: all 0.2s;
}

.shop-item:hover:not(:disabled) {
    background-color: var(--primary-color);
}

.shop-item:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    border-color: #475569;
}

.shop-item.purchased {
    background-color: var(--success-color);
    border-color: var(--success-color);
}