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

:root {
    --bg-primary: #1a1a1a;
    --bg-secondary: #2a2a2a;
    --bg-tertiary: #3a3a3a;
    --text-primary: #ffffff;
    --text-secondary: #b0b0b0;
    --border-color: #404040;
    --accent-color: #10b981;
    --accent-light: #34d399;
    --danger-color: #ef4444;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

body.light-mode {
    --bg-primary: #f4f5f7;
    --bg-secondary: #ffffff;
    --bg-tertiary: #eef0f3;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --border-color: #d0d0d0;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    transition: background-color 0.3s, color 0.3s;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 32px;
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 10;
}

.header-left { display: flex; align-items: center; gap: 20px; }

.back-btn {
    font-size: 13px;
    color: var(--text-secondary);
    text-decoration: none;
    padding: 6px 12px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    transition: all 0.2s;
    white-space: nowrap;
}

.back-btn:hover { color: var(--accent-color); border-color: var(--accent-color); }

.brand { display: flex; align-items: center; gap: 12px; }

.brand-logo {
    width: 36px;
    height: 36px;
    background-color: var(--accent-color);
    color: #ffffff;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    font-weight: 800;
    flex-shrink: 0;
}

.brand-text { display: flex; flex-direction: column; }
.brand-name { font-size: 16px; font-weight: 700; line-height: 1.2; }
.brand-tag { font-size: 11px; color: var(--text-secondary); text-transform: uppercase; letter-spacing: 0.7px; }

/* Theme Toggle */
.theme-toggle {
    width: 48px;
    height: 26px;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 13px;
    cursor: pointer;
    display: flex;
    align-items: center;
    padding: 3px;
    transition: all 0.3s;
}

.theme-toggle.light { justify-content: flex-end; }

.theme-toggle-circle {
    width: 20px;
    height: 20px;
    background-color: var(--text-primary);
    border-radius: 50%;
    transition: all 0.3s;
}

.theme-toggle.light .theme-toggle-circle { background-color: var(--accent-color); }

/* Main — vertically centered */
.main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px 32px;
    gap: 16px;
    max-width: 600px;
    width: 100%;
    margin: 0 auto;
}

/* Drop zone card */
.upload-card {
    width: 100%;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    overflow: hidden;
}

.upload-area {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 32px;
    border: 2px dashed var(--border-color);
    border-radius: 16px;
    cursor: pointer;
    transition: all 0.2s;
    gap: 8px;
    text-align: center;
}

.upload-area:hover, .upload-area.drag-over {
    border-color: var(--accent-color);
    background-color: rgba(16, 185, 129, 0.05);
}

.upload-icon { font-size: 52px; margin-bottom: 6px; }
.upload-title { font-size: 18px; font-weight: 700; color: var(--text-primary); }
.upload-sub { font-size: 14px; color: var(--text-secondary); }
.upload-hint { font-size: 12px; color: var(--text-secondary); margin-top: 4px; }

#fileInput { display: none; }

/* Selected file card */
.selected-card {
    width: 100%;
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 16px 20px;
    background-color: var(--bg-secondary);
    border: 1px solid var(--accent-color);
    border-radius: 12px;
}

.selected-icon { font-size: 28px; flex-shrink: 0; }

.selected-info { flex: 1; overflow: hidden; }

.selected-name {
    font-size: 14px;
    font-weight: 600;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.selected-size { font-size: 12px; color: var(--text-secondary); margin-top: 2px; }

.change-btn {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 12px;
    font-weight: 500;
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
    flex-shrink: 0;
}

.change-btn:hover { border-color: var(--text-secondary); color: var(--text-primary); }

/* Buttons */
.btn {
    padding: 10px 22px;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    white-space: nowrap;
    flex-shrink: 0;
}

.btn-primary { background-color: var(--accent-color); color: #ffffff; }
.btn-primary:hover { opacity: 0.9; }

/* Error */
.error-msg {
    font-size: 13px;
    color: var(--danger-color);
    background-color: rgba(239, 68, 68, 0.1);
    border: 1px solid rgba(239, 68, 68, 0.25);
    padding: 10px 16px;
    border-radius: 8px;
    width: 100%;
    text-align: center;
}

@media (max-width: 480px) {
    .page-header { padding: 12px 16px; }
    .main { padding: 24px 16px; }
    .upload-area { padding: 40px 20px; }
    .selected-card { flex-wrap: wrap; }
    .btn { width: 100%; justify-content: center; }
}